最新刊期
卷 ， 期 3 ， 2008
- 摘要：Combining living anionic polymerization and atom transfer radical polymerization (ATRP),well-defined comb-like branched polymers having one branch in each repeating unit were successfully synthesized by the coupling reaction of living PS and PI anions with 1,1-diphenylethenyl (DPE) groups along PS backbone.ATRP of 4-vinylbenzyloxy benzophenone (Sc) carried out in diphenyl ether at 130℃ using PhCH2Cl as an initiator and CuCl/2,2′-bipyridine complex as a catalyst led to PSc with benzophenone pendant groups.The molar ratio of PhCH2Cl,CuCl and 2,2--bipyridine used in ATRP was 1∶1∶3.The PSc was then converted to the corresponding PSe bearing DPE pendant groups viaWittig reaction,and PSe was used as a polymer backbone.Finally the coupling reaction of living PSLi or PILi prepared by the polymerization of styrene or isoprene via living anionic polymerization using n-BuLi as initiator in THF with DPE groups of PSe was carried out at -78℃ to form the desired comb-like branched polymers PSe-g-PS or PSe-g-PI.The resulting comb-like branched polymers and precursors were characterized by IR, 1H-NMR,GPC and SLS measurements in detail.The peak at higher molecular weight ascribed to the comblike branched polymer in the GPC profile of crude comb-like branched polymer was sharp monodal and very narrow,suggesting a homogeneous and clean grafting.The apparent molecular weight of the comblike branched polymers determined by GPC was not reliable due to its branching structure.The absolute molecular weights of these polymers were therefore determined by SLS measurements.The values were much closed to the corresponding theoretical ones calculated assuming all the living chains were coupled with DPE groups (living chains were lack or equal) or all the DPE groups were consumed (living chains were excess),suggesting that the grafting is nearly complete.The grafting efficiency could be calculated by comparing the molecular weights by SLS and the corresponding theoretical ones.Furthermore,the grafting efficiency was also proved to be almost quantitative by comparing 1H-NMR spectrum of comb-like branched PSe-g-PS and PSe.The effect of living chains and DPE groups molar ratio ([PSLi]0/[DPE]0) on grafting efficiency was discussed.When [PSLi]0/[DPE]0 varied from 0.7 to 1.2,the grafting efficiency increased from 65.5% to 101%.The results showed the coupling reaction of living chains and DPE groups was highly effective and proceeded until all the DPE groups were consumed,and the grafting efficiency could be controlled viachanging the feed molar ratios of living chains and DPE groups.Moreover,when excess living polymers were used,the effect of molecular weights of PSe and PSLi or PILi on graft efficiency was also discussed.When the Mw of PSe was smaller than 10000 s,and the Mw of PSLi varied from 4200 to 11200,almost quantitative grafting efficiency could also be achieved.When living chains was PILi,the similar results were obtained.In conclusion,all the results demonstrate that the method by coupling reaction of living polymer anion with DPE groups along backbone is very effective for the synthesis of well defined comb-like branched polymers.
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发布时间：2021-03-19 - 摘要：The grafting polymerization of styrene on micronsized silica gel particles was performed in solution polymerization system with the manner of “grafting from”,and grafting particles PSt/SiO2 were obtained.Chloromethylation reaction for the polystyrene grafted on silica gel particle surfaces was allowed to be carried out by using a novel chloromethylation reagent,1,4-bis(chloromethoxy)butane (BCMB),and chloromethylated polystyrenegrafted silica gel particles,CMPS/SiO2,were prepared and these composite particles also can be called as “composite-type chloro-sphere”. The grafting degree of PSt/SiO2 was analyzed with thermaogravimetric analysis (TG),and the morphology of PSt/SiO2 particles was examined with scanning electron microscope (SEM).The chemical structure and composition of CMPS/SiO2 particles were characterized using infrared spectrum (FTIR) and Volhard method.The effects of various factors on the chloromethylation reaction of PSt/SiO2 were mainly examined.The experimental results show that the method for preparing the composite-type chlorosphere CMPS/SiO2 in this study not only is environmentally friendly,but also is easy to be controlled.Various factors,such as reaction time,solvents,catalysts and their used amount and the use level of BCMB will influence the preparation of the composite particle CMPS/SiO2 greatly.The effects of these factors exhibit in two aspects:(1) they affect the chloromethylation degree of CMPS/SiO2; (2) they inhibit or accelerate the FriedelCrafts crosslinking reaction between polystyrene macromolecular chains grafted on the surfaces of silica gel particles.The CMPS/SiO2 with about 16 wt% of chlorine content (based on the grafted polystyrene) can be prepared when the reaction was carried out at room temperature for about 8 h using CH2Cl2 as solvent and SnCl4 as catalyst.
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发布时间：2021-03-19 - 摘要：The dynamics of the detachment of single polyethylene (PE) chains from a strong adsorption surface is investigated by the steered molecular dynamics method (SMD).Our simulations use the unitedatom (UA) model of PE chains,which regards each CH2 and CH group as a monomer.Due to the significant reduction of the number of the degrees of freedom,the UA model allows one to explore longer chains or a larger number of systems within the limited computational time.In the previous investigations with SMD,the simulation is performed only once,and the statistical properties can not be discussed.In this work,the statistical behavior of single PE chains pulled from the strong adsorption surface is investigated with the SMD and MC method.There exists a long force plateau for the curve of average force probed by spring f,which agrees well with the experimental results.The relationship between the average forcef and the pulling velocity v shows two distinctive regions:a weak dependence region as v0.001 nm/ps,and a strong dependence region as v0.001 nm/ps. Remarkably,the PE chain manifests force hysteresis under sequential stretching and releasing.The area of the hysteresis also increases with the velocity v. Force-extension curves display hysteresis because the velocity at which the polymer chain is stretched and released exceeds the velocity of unfolding and folding of the polymer at equilibrium at that extension.If the stretchingreleasing had been done at a very low velocity used in the experiment,the stretching or releasing curves will converge toward a single intermediate curve representing the equilibrium process.Some results in our simulation agree well with the available experimental results,while the others may provide some insights into the related processes and further experimental investigatiozns.
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发布时间：2021-03-19 -
Study of Nano-Silica/Fluorinated acrylate Copolymer Hybrid Emulsion and the Pol ymerization Kinetics
摘要：Perfluorinated polymers are of high scientific and technological interest owing to their unique characteristics.However,their utilization is limited due to their poor cohesiveness,film-forming properties and high cost.When perfluorinated polymers are incorporated with polyacrylate, remarkable properties are exhibited with higher performance price ratio; that is,oil and water repellency of the former is unmitigated while the mechanical strength and cohesiveness of the latter are retained.As an inexpensive functional component,incorporated silica can shield polymeric matrix from the UV,while reinforcement and improved thermal stability are achieved,as well as better rinse-resistance,perdurability and self-cleanness effects. In this paper,nano-silica and poly(MMA-co-nBA-co-FA) were combined with covalent bonds.Not only extraordinary properties derived from each individual component were retained,but also a more intimate cooperation was provided between the twos,through an environment-friendly method. At first,the monodisperse silica was prepared in ethanol according to the well-known Stober procedure,followed by modification via addition of γ-methacryloxy propyltrimethoxysilane (MPS).Then,the nano-silica/poly(MMA-co-nBA-co-FA) hybrid emulsion was prepared via insitu emulsion polymerization in the presence of MPS-grafted silica. The chemical compositions and morphologies of both nano-silica and silica/poly(MMA-co-nBA-co-FA) nanocomposites (NPs) were characterized by Fouriertransform infrared (FT-IR) spectrometry and transmission electron microscopy (TEM),respectively.From TEM images,it was obvious that uniform spherical nano-silica was obtained,with average diameter of 20 nm.FT-IR effectively proved the occurrence of MPS-grafting reaction.According to the amount of MPS added,the MPSgrafted density of nano-silica was determinated as 0.1716 μmol/m2. Off-centre core-shell structures of silica/poly(MMA-co-nBA-co-FA) NPs were confirmed by TEM images.Approximately 50% of NPs had more than one single core due to the congregating of smaller particles when the diameters of the core were not larger than 100 nm.Under a low MPS-grafted density,not all of monomers were polymerized and connected with MPS on the grafted silica,and most of the polymer chains were twisted and absorbed around the core particles,followed by copolymerization with polymer layer copolymerized with MPS,resulted in an off-centre core-shell structure ultimately. Thermal stability of silica/poly(MMA-co-nBA-co-FA) NPs was studied via thermal gravimetric analysis (TGA).The results showed that higher initiative decompose temperature was achieved with more nano-silica incorporated,which implicated the successful encapsulation of silica into NPs,as well as enhanced thermal stability. The surface properties of the latex films produced from silica/poly(MMA-co-nBA-co-FA) NPs were also investigated by contact angle method and water absorption measurements.Obviously,the incorporation of silica and FA contributed to degressive surface-free energy,with a minimum value of 9.8 mN/m.Similarly,water absorption ratio decreased with increasing contents of nano-silica and FA.What worth noting was the abnormal polar and disperse component of surface-free energy,which might be attributed to nano-silica’s incorporation and distribution while film-forming. Besides these,the kinetics of in situ emulsion polymerization,in which MPS-grafted silica with a low grafted density was introduced,had been investigated in details.The results can be summarized as follows: Rp∝［FA］0.25［SiO2］0.31［I］0.66［E］0.757 while ［SiO2］ 8.9 × 10-2 mol#8226;L-1, and Rp∝［FA］0.25［SiO2］-1.33［I］0.66［E］0.757 while ［SiO2］8.9×10 -2 mol.L -1.The overall activation energy of the polymerization was calculated to be 83.15 kJ/mol.- 21
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发布时间：2021-03-19 - 摘要：Amphiphilic azo polymers with different azo chromophores and degree of functionalization (DF) were synthesized,and colloidal spheres of the polymers were prepared by gradual hydrophobic aggregation in selective solvents.To obtain suspensions of colloidal spheres,the required amounts of water were added into the THF solutions at a certain stirring rate.As the water content reached ca.70 vol%,an excess of water was added into the suspensions to “quench” the formed structures.The obtained suspensions of colloidal spheres were sealed after THF was completely volatilized and were characterized by DLS and UV-Vis spectroscopy.The size and size-distribution of colloidal spheres were measured by using a DLS/SLS-5022F laser light scattering apparatus.Before the measurement,the sample was clarified by a 0.45 μm Millipore filter to remove dust,and all the DLS measurements were carried out with 90° scattering angle.UV-Vis spectroscopy was used to study the azo chromophore structure variation in the colloid formation process by measuring the parameters such as the trans-to-cis photoisomerization rate and the isomerization degree at the photostationary state.In the photoresponse experiments,the sample was irradiated by a 365 nm UV light source,and the light intensity was 7000 mV/cm2 at a distance of 38 cm and 21000 mV/cm2 at a distance of 5 cm,respectively.In our experiment,the sample was 15 cm away from the UV light,and the temperature of the environment was 30℃.The influences of molecular structure and preparation conditions on the size and photoresponsive properties of the colloidal spheres were studied in some detail. The result shows that the functional group type and DF as well as the preparation conditions (initial polymer concentration,the rate of water addition, etc.) have significant effects on the size and photoresponsive properties of the colloidal spheres. The size of colloidal spheres increases with the increase of DF and initial concentration,but decreases with the increase of the rate of water addition.The photoinduced isomerization rate of poly{2-4-(4-ethoxyphenylazo)phenoxy］ethyl acrylate-co-acrylic acid} (PEAPE) colloids is higher than that of poly{2-[-4-(4-cyanophenylazo)phenoxy］ethyl acrylate-co-acrylic acid} (PCNPE) colloids.The PEAPE colloids with higher DF show a slower photoisomerization rate. The photoinduced isomerization rate of the colloids decreases with the increase of initial concentration and the decrease of the rate of water addition.The possible mechanism for the influence is also discussed based on thermodynamics and kinetics consideration.It is believed that the colloidal spheres form through a self-assembling process controlled by the dynamic conditions.For high initial concentration and slow water dropping rate,more polymer chains tend to aggregate on the compact cores formed from the most hydrophobic chains as the water content is above the critical water content (CWC).Moreover,the polymeric chains had chance to rearrange themselves to form stable and compact structures due to the slow rate of water addition.On the other hand,as the rate of water addition increased,the polymeric chains attached to the cores were quickly “frozen" before they could completely adjust their conformations.Also,they could form new less compact cores so as to weaken the continuous aggregation probability.As a result,the formed aggregates had loose structures,and the photoinduced isomerization rate was relatively fast.
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发布时间：2021-03-19 - 摘要：Liquid crystal (LC) polymers have been extensively investigated for their unique properties and many potential applications.Introducing cinnamate functional groups into the polymers can combine the mesogenic properties of LC polymers with the photo-crosslinking ability of the photosensitive groups.In this work,a methacrylatebased monomer (M1) functionalized with mesogenic biphenyl and cinnamate groups was synthesized via nucleophilic substitution and DCC esterification reactions following a newly designed synthetic route.The overall yield was much higher than that reported before.Another methacrylate monomer (M2) functionalized with mesogenic biphenyl and n-butyl end group was also synthesized in the same way.The homopolymers of the two monomers and a series of new liquid crystalline copolymers have been synthesized by solution radical polymerization with different feed ratios of the two monomers.The structures of the monomers and the polymers were characterized by 1H-NMR and FT-IR.1H-NMR results revealed that the contents of M2 in all of the copolymers were higher than the corresponding feed ratios,which indicateded that M2 was more reactive than M1. The liquid crystalline (LC) phase behavior was investigated by differential scanning calorimetry (DSC),polarized optical microscopy (POM) and wide angle and small angle X-ray diffraction (WAXD and SAXD).The monomer with cinnamate group as its end (M1) exhibited no LC behavior while the monomer with n-butyl as end group (M2) showed smectic LC behavior.The homopolymer of M1(P1) and the homopolymer of M2(P9) showed weak anisotropy and thermotropic smectic LC phase,respectively.The copolymers (P2～P8 with increasing ratio of M2 to M1) all showed thermotropic LC behavior.The copolymers P2～P5 exhibited characteristic features of nematic LC phases and P6～P9 showed smectic phase behavior.With the increase of the content of M2 in the copolymers,the glass transition temperature,the melting point and the clearing point increased. As the cinnamate functional groups in the LC polymer can be crosslinked through photo-induced ［2+2］ cycloaddition reaction,the polymer can be used to prepare LC elastomers.
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发布时间：2021-03-19 - 摘要：Polyaniline (PANI) is one of the most promising conducting polymers for its high environmental stability,tunable electrical properties and relatively low cost.Anyway,one of the problems associated with its successful application in many areas,such as organic conductors,actuators,electromagnetic shielding,light-emitting diodes and gas-separation membranes,is the difficulty in processing of this material due to its very low solubility in different organic solvents.One of the approaches to improve the processability of polyanilines in solvents is to prepare them by chemical emulsion polymerization of aniline in the presence of various surfactants such as camphorsulphnic acid(CSA),dinonylnaphthalenesulphnic acid (DNNSA) and dodecylbenzenesulphnic acid (DBSA),which was used as emulsifier and dopant,simultaneously.However,many researches have focused on the influences of the aniline and/or surfactant concentration,time and temperature etc on the conductivity and solubility of the resulting polyanilines,there are no detailed reports on the monitoring of the emulsion polymerization process and the emulsion polymerization mechanism of aniline in the presence of surfactant,that is DBSA.And the location and morphology of aniline or its anion in the reaction medium are important that they can give the useful information of reaction mechanism and properties of the final product. In this report,the emulsion polymerization of aniline (Ani) in a system consisted of dodecylbenzenesulphonic acid (DBSA)-water-aniline was carried out using ammonium peroxydisulfate（APS）as oxidant.The microscope and SEM was used to monitor the polymerization process.The effects of the molar ratio of DBSA/Ani/APS and the concentration of DBSA and Ani on the morphologies of polymerization systems and the conductivity of the resulting polyanilines were investigated.It shows that in all cases Ani and DBSA combined and formed micro-rods before the polymerization,which became shorter and fewer during the polymerization process,meanwhile the resulting polyanilines possessed granular particle morphology.Therefore we proposed that the polymerization mechanism of aniline in the DBSA-water-aniline system was as follows:DBSA first reacted with aniline to give DBSA-aniline salts,which were insoluble in water and self-assembled into micro-rod aggregates before the emulsion polymerization occurred.Any way the emulsion polymerization of aniline in DBSA/water system was just took place in the micelles as the excess DBSA in the reaction system could form micelles solubilized aniline.With proceeding polymerization reaction,DBSA-aniline salts in the micro-rods were dissolved and diffused into the latexes to give resulting polyaniline doped by DBSA in granular particle morphology.
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发布时间：2021-03-19 - 摘要：The isomeric effects of dianhydride on the crystalline properties of polyimide were reported,it was a continuation of isomeric polyimides studies in our group.A series of molecular-weight-controlled isomeric polyimides powders based on three dianhydride isomers,3,3′,4,4′-oxydiphthalic dianhydride (4,4′-ODPA),2,3′,3,4′-oxydiphthalic dianhydride (3,4′-ODPA) and 2,2′,3,3′-oxydiphthalic dianhydride (3,3′-ODPA),and 4,4′-oxydianiline (ODA) were prepared by traditional two-step method in DMAc,and phthalic anhydride (PA) was used as end-capper.Wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) were used to investigate the crystallization behavior of isomeric polyimides.The annealing temperature,annealing time,external force shearing and molecular weight effects on the crystallization of isomeric polyimides were studied.The results proved that 4,4′-ODPA/ODA-based polyimide powder was amorphous at room temperature and could crystallize during annealing or shearing process above Tg.The crystallization of 4,4′-ODPA/ODA-basedpolyimide was enhanced by increasing the annealing temperature and time,decreasing molecular weight or pushing shearing above Tg.Two melting endo-peaks appeared evidently when the annealing temperature was below 300℃.The two melting peaks tended to be close to each other with the increase of annealing temperature,and only one melting peak was found when annealing temperature reached 370℃.The higher melting temperature of 4,4′-ODPA/ODA-based polyimide was aroud 370～380℃,however,this polyimide was difficult to recrystallize once melted.This polyimide was annealed at 370℃ for different times,the amorphous as-prepared samples had crystallized after annealing at 370℃ only in 1 min,besides the crystallinity was increased with the increase of the annealing time,but no crystalline form change was found.The polyimide with low molecular weight was easy to crystallize.It can be seen that the polyimide with ηinh of 0.34 dL/g showed the highest endo-peak,the polyimide with the ηinh of 0.64dL/g showed the smallest endo-peak,while the polyimide with the ηinh of 1.1 dL/g exhibited completely amorphous.Pushing shearing at 250,260 and 300℃ for 100 min with a shear rate of 2 s-1 indicated that the shearing process indeed enhanced the crystallization of polyimide above 260℃,although the effect was not so obvious.While at 250℃ or lower temperatures the shearing almost did not effect at all.The isomeric polyimides based on 3,4′-ODPA/ODA and 3,3′-ODPA/ODA were synthesized with the comparable inherent viscosity with 4,4′-ODPA/ODA.They were tested after the same treatment as we had did for 4,4′-ODPA/ODA,such as different annealing temperature,annealing time,shearing,etc.,however,the two isomeric polyimides just as expected remained amorphous.
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发布时间：2021-03-19 - 摘要：Fe3O4 magnetic nanoparticles have been widely used in biomedical applications such as magnetic resonance imaging contrast reagent,tissue repair,immunoassay,hyperthermia,drug delivery and cell separation,etc.due to their specific magnetic properties.All these applications require high magnetization values,nanostructure size with overall narrow particle size distribution and special surface coating of the magnetic particles.The latter not only makes Fe3O4 magnetic nanoparticles nontoxic and biocompatible to organism but also provides more chemical selections for molecular device designs.In this paper,Fe3O4 magnetic nanoparticles with mean diameter of about 25 nm were prepared by a precipitation method with ferric chloride as starting material,which was partially reduced to ferrous salts by Na2SO3 before alkalinizing with ammonia.XRD analyses showed that the crystal lattice of the magnetic nanoparticles was face centered cubic (fcc) structure.Afterwards,Si—H bonds were imported to the surface of Fe3O4 magnetic nanoparticles by chemical treatment,and then a magnetic-initiator with bromine end groups was prepared from a selective hydrosylation.The resultant initiator was further used to polymerize acrylamide through atom transfer radical polymerization (ATRP).The grafted polyacrylamide on the surface of Fe3O4 magnetic nanoparticles exhibited the characteristics of ATRP-controlled molecular weights and narrow polydispersity.The molecular mass of polyacrylamide could be modulated by controlling the molar ratio of monomer acrylamide to magnetic-initiator.When the molar ratio was 90,the number average molecular weight was 6440,the polydispersity was 1.19,the molar grafting ratio of polyacrylamide was about 5%， and the thickness of the surface polymer coatings was about 10 nm.Becauseit was difficult to directly characterize the surface polyacrylamide of magnetic nanoparticles,so a linear polyacrylamide in the solution was prepared through ATRP to investigate the polymeric structures.Both 1H-NMR and FTIR exhibited the characteristics of polyacrylamide.DSC measurements showed that the decomposition temperature (Td) of the surface polyacrylamide of magnetic nanoparticles was 242℃,and the glass transition temperature (Tg) was 102℃,which apparently decreased as compared to that of linear polyacrylamide (Tg=165℃).This was because the star structure weakened the interaction of polyacrylamide molecules and reduced the cohesive energies of materials and then made the polymeric chains move more easily.The specific saturation magnetization of polyacrylamidemodified Fe3O4 magnetic nanoparticles was 58.5 emu.g-1,which declined 20% compared to that of the non-modified Fe3O4 nanoparticles.The graft of polyacrylamide on the surface of Fe3O4 magnetic nanoparticles can improve the biocompatibility of magnetic nanoparticles,and also endow the particles with more chemical selectivities for the further surface functionalization of magnetic nanoparticles,so these polyacrylamidemodified Fe3O4 magnetic nanoparticles will provide a platform for potential applications in biomedicines.
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发布时间：2021-03-19 - 摘要：The temperatureinduced variation of the conformational behavior and the packing structure of alkyl chains in n-nonadecane, N-octadecylated polyethyleneimine (PEI18C) and N-octadecylated poly(p-benzamide) (PBA18C) were investigated with FTIR spectroscopy and other techniques.The main aim is to in-depth understand the specific aggregation structure of alkyl side chains in the comblike polymers.N-alkylation reactions on polyethyleneimine (PEI) and poly(p-benzamide) (PBA) backbone were carried out in homogenous solutions composed of octadecyl bromide and polymer substrate.According to the results of nuclear magnetic resonance (NMR) and elemental analysis measurements,the N-substitution degree was obtained, i.e. 47% for PEI18C and 97% for PBA18C,respectively.The relative intensity of the conformation bands of methylene group at 1463 cm-1 and 1470 cm-1 was utilized to investigate the conformation transition behavior of PEI18C and nonadecane in the heating process.The results indicated that the octadecyl chains of PEI18C exhibited different conformation transition process compared with those of nonadecane.The variation of the rocking bands of methylene groups implied that the ordered packing structure of the octadecyl chains in PEI18C had much more slower transition velocity and complicated variation process than those of pure nonadecane.Based on the differences among the above mentioned IR spectral bands of PEI18C,PBA18C and nonadecane,the ordered degree of the conformation and the packing structure of the alkyl chains were compared.The alkyl side chains of PEI18C and PBA18C were found to pack into aggregation structure with different ordered degree,originating from the confinement and rigidity difference of the main chain.After melting,unlike nonadecane,the alkyl chains of PEI18C and PBA18C can not get into totally random amorphous state.The above results reveal that the conformational changes,packing structure of CH2 groups and their phase transition behavior in the confined and nonconfined state are obviously different in all the above three cases,which might be attributed to the different mobility of alkyl side chains under the aforementioned confinement condition.Moreover,the different main chain structural characteristic i.e. flexibility or rigidity,also has extensive influence on the conformational changes and packing structure of alkyl groups grafted on the PEI and PBA backbone.The main reason can be ascribed to the different conformation adjustment ability of the PEI and PBA backbones.
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发布时间：2021-03-19 - 摘要：Inspired by biomineralization in nature,organic-inorganic hybrid SiO2 particles were synthesized in situ by a novel route,which is definitely superior to traditional synthesis route of organicinorganic hybrid materials due to environmentfriendly,simple,economic,etc.Besides experimental convenience,hybrid particles obtained possess sophisticated structures due to polymer microgel as templates that controls silica deposition.In our investigation,polyamine mocrogel was selected as templates which induced the formation of sophisticated structure of hybrid particles that possessed dramatic surface and inner properties.The poly(acrylamide-co-dimethylaminoethylacrylate-methyl chloride) (P(AM-co-DMC)) microgel was prepared by inverse emulsion polymerization in the presence of a crosslinker.By controlling the swallowing degree of microgel,the silica deposition was conducted by simply stirring a mixture aqueous dispersion of the microgel and tetramethyl orthosilicate (TMOS) as a stable silica source at pH 7.2 and 20℃.We found that there was no evidence for nontemplated silica structures,which suggests that silica deposition was well-controlled to occur in the polymeric network of microgel template.The obtained particles were carefully characterized with FT-IR spectroscopy,dynamic lighter scattering (DLS),transmission electron microscopy (TEM),energy dispersive analysis system of X-ray (EDX),scanning electron microscopy (SEM).In FT-IR and EDX spectra,it’s indicated that microgel/SiO2 hybrid particles was formed,and pure silica particle was retained after calcinations.Studies on mean diameter,morphology and surface properties of hybrid particles indicated that microgel played a leading role in the process of silica deposition,which determined the morphology and dimension of hybrid particles.Silica deposition proceeded in the microgel microenvironment,and organicinorganic hybrid construction was formed.Silica nano-particles were located in the whole microgel possessing good mechanical stability that kept morphology of templates after calcinations.TMOS also has influence on hybrid particles.Low amount of TMOS led to rough surface while smooth surface was obtained by increasing TMOS quantity.The roughness of surface increased after calcinations.Either the hybrid microgelsilica particles or the calcined silica particles exhibited nanostructural character (porosity),and the nanostructures in the particles can be well controlled by tuning the level of TMOS addition,suggesting the potential applications for the encapsulation and controlled release for drug and other active molecules.
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发布时间：2021-03-19 - 摘要：Two regioregular poly(p-phenyleneethynylene-alt-m-phenyleneethynylene)s bearing (-)-trans-myrtanoxyl side groups with different substitution patterns were designed and synthesized, e.g. Myr-PMPE-1 and Myr-PMPE-2.In order to obtain regioregular polymer,a novel AB type monomer 1-((5-bromo-2-myrtanoxyphenyl)ethynyl)-4ethynyl-2,5-myrtanoxybenzene and a novel AA type monomer 2,2′-(2,5-dimyrtanoxy-1,4-phenylene)bis(ethyne-2,1-diyl)bis(4-bromo-1-myrtanoxybenzene) were designed and synthesized by the strategy based on the different activity between bromo and iodo-benzene in Sonogashira reaction.By Sonogashira polymerization,the AB type monomer gave Myr-PMPE-1,in which the side chiral groups were distributed uniformly along the backbone.On the other hand,the obtained AA type monomer was polymerized with 1,4-diethynyl-2,5-dimyrtanoxybenzene to give Myr-PMPE-2,in which the distribution of the side chiral groups was alternatively crowd and loose.Both of these two polymers showed no CD signal in solution because of their good solubilities.Then,the investigations of chiroptical properties of these two polymers were carried out in the form of spincast films.The films were annealed above the glass temperature of the corresponding polymer,and the effects of annealing temperature and time on the properties of the films were investigated by UV-Vis absorption,fluorescence and circular dichroism spectra.The results showed that annealing treatment had no significant effect on the properties of Myr-PMPE-1,including UV-Vis absorption,fluorescence and optical activity.The maximum absolute value of dissymmetry factor (|gmax|) was 1.62×10-4. On the other hand,annealing treatment significantly affected the properties of Myr-PMPE-2.Without annealing or being annealed below 100℃,the Myr-PMPE-2 films showed almost no Cotton effect.In contrast,when annealed above 120℃,the absorption and emission of MyrPMPE2 film slightly red shifted with increasing annealing temperature and annealing time,and most importantly,the intense of CD signals increased significantly,and the optical activity of Myr-PMPE-2 films increased obviously.After annealing at 140℃ for 4 h,|gmax|of Myr-PMPE-2 film was up to 3.07×10-3,about one order of magnitude higher than that of Myr-PMPE-1 film.These observations indicate that the substitution pattern of the chiral side groups has significant effect on the chiroptical properties of chirally substituted conjugated polymers.The obtained results can contribute to the design of chiral conjugated polymers with high optical activity.
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发布时间：2021-03-19
Research Article
- 摘要：A new strategy was developed for preparation of high fluidfy nylon 6 on a large scale.Generation 1,2,3 (G1,G2,G3) polyamidoamine (PAMAM) dendrimers reacted with p-phthalic acid by equimolar terminal groups in water solutions, respectively，and mother salt solutions were then prepared.The high fluidity nylon 6 was prepared with suitable quantity of mother salt solution,end capping agent (acetic acid) and ε-caprolactam by in situ polymerization.By changing the quantity of mother salt solution or the generation of PAMAM dendrimers,different samples of high fluidity nylon 6 were obtained.Blue shifts were found for the peaks of NH (γN—H and 2δN—H ) of the high fluidity nylon 6 compared with pure nylon 6 in the IR spectra.Compared with pure nylon 6,the samples of high fluidity nylon 6 with low content of PAMAM units (0.3 wt%～0.5 wt%) had greater MFI,the value of MFI was improved about 70%～90%.It was also found that there was a drastic increment in MFI when the content of PAMAM units in PA6 matrix increased from 0.5 wt% to 1.2 wt%,while the molecular weight of the high fluidity nylon 6 did not decrease.For the high fluidity nylon 6 with low content of PAMAM units (0.3 wt%～0.5 wt%),the tensile strength did not decrease while the elongation at break decreaed (ca.20％～35%)， and the izod impact strength of different kinds of high fluidity nylon 6 increased.DSC thermograms of nonisothermal crystallization exhibited that the peak temperature of high fluidity nylon 6 was lower than that of pure nylon 6,and the peak of crystallization curve broadened comparing with the pure nylon 6 at the same crystallization condition,which broadened more with increasing the generation or the content of PAMAM units.Broader peak means the crystallization rate was decreased and the fluidity was improved,which benefits molding of small parts with thin walls or precision parts.
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发布时间：2021-03-19 - 摘要：A novel functionalized dendronized polyamide decorated with a lot of bromomethyl groups in the periphery has been reported by the macromonomer route.The resulting polyamide had both a polyamide backbone and polyamide dendrons.A new activating procedure of thionyl chloride as an activating agent was adopted to synthesize the dendrons,macromonomer and polyamide.This activating procedure eliminated the protection/deprotection procedure and reduced side reactions.The syntheses of the products adopted the method of the convergent synthesis which was carried out by a two-step method involving1the activation of carboxylic groups with thionyl chloride and [STHZ]2 condensation with an unprotected AB2 building block.The structures of the products were confirmed by Fourier transform infrared and NMR spectral analyses.The gel permeation chromatography analyses (GPC) of the resulting polyamide showed a typical weight-average molecular weight (Mw) of 5.01×10.4 versus polystyrene and a polydispersity of 2.74.The solubility of the resulting polyamide was improved remarkably because of the introduction of the dendritic fragments and the existence of the periphery functional groups.The resulting polyamide could easily dissolve in aprotic polar solvents such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc),dimethyl sulfoxide (DMSO),N-methyl-2-pyrrolidone (NMP) and sulfuric acid (H2SO4).The inherent viscosity of the resulting polyamide was low because of the presence of the dendritic fragments, and it was 0.09 dL/g.The thermal properties were also studied by thermogravimetric analysis (TGA), and the result showed that the resulting polyamide had good thermal properties.Because of a lot of bromomethyl groups in the periphery,the resulting polyamide could be used as a initiator for atom transfer radical polymerization (ATRP) to synthesize “hairy” functional derivatives and could also be applied in many fields through converting bromomethyl groups into other desired groups such as amino and hydroxyl groups.
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发布时间：2021-03-19 - 摘要：Hydroxy-telechelic aliphatic (co)polyesters are important building blocks of biodegradable multiblock copolymers which can be used as biodegradable elastomers and biodegradable shape memory polymers (BSMPs).For BSMPs,the transition or switch temperature at which the shape memory effect takes place is determined by the thermal trasition temperature of the reversible phase or soft segments, and the shape memory properties and mechanical properties are maily affected by the condensed state of the fixed phase or hard segments.Therefore,the thermal transition temperatures of hydroxy-telechelic aliphatic (co)polyesters are critical parameters for successful design of BSMPs.This article aims to report the relationship among the thermal transition temperature of two important hydroxy-telechelic aliphatic copolyesters,poly(L-lactide-co-glycolide) (PLLGA) and poly(ε-caprolactone-co-glycolide) (PCG),and their molecular weight and copolymer composition. Hydroxy-telechelic PLLGA and PCG are synthesized via ringopening copolymerization of L-lactide and glycolide (LLA/GA) and ε-caprolactone and glycolide (CL/GA) using 1,4-butanediol as initiator and stannous octoate as catalyst at 140℃.After dissolving in chloroform,precipitated from methanol and drying under vacuum at 75℃ for 48 h,purified PLLGA and PCG were obtained and characterized by FTIR,1H-NMR,GPC and DSC. The polymerization took place in a living/controlled manner,and the molecular weight was adjusted by the monomer/initiator ratio in the range of 2000～14000.The polydispersity index ranged from 1.1 to 1.3.The GA content in the copolymers is of 0～0.22 for PLLGA and 0～0.32 for PCG and can be adjusted by the GA content in monomer feed (GA,0～0.2).The contents of GA in copolymers are higher than GA because of higher reactivity ratio of GA than LLA and CL.For convenience，GA was used to denote the copolymer composition.The FTIR and 1H-NMR spectra indicate that the copolymers are hydroxy-telechelic. The DSC results indicate that the copolymers with above mentioned copolymer composition and molecular weight are all semicrystalline polymers.The melt temperatures (Tm) of both PLLGA and PCG were determined from the second scan.The Tm ranged from 37℃ to 58℃ for PCG and from 80℃ to 162℃ for PLLA.They increased with increasing the molecular weight but decreased with increasing the copolymer composition.The glass transition temperature (Tg) of PLLGA was obtained from the second scan and ranged from 35℃ to 54℃.It also increased with increasing the molecular weight but decreased with increasing the copolymer composition.By ploting Tg and Tms with the reciprocal of number average molecular weight (Mn),linear relationships,Tg＝Tg(∞)-K/Mn and Tm＝Tm(∞)-K′/Mn,are observed.For Tm,the interceptions Tm(∞) are linearly decreased with increasing GA,but the slope K′ is independent of GA.Therefore,experiential linear equations Tm＝Tm(H)-AGA-K′/Mn have been established to describe their relationship,in which Tm(H) is the melt temperature of PLLA and PCL homopolymers.For PLLGA,the values of Tm(H),A and K′ are 166.9,129.5 and 1.48×105,respectively.For PCG,they are 60.4,82.0 and 2.92×104,respectively.From these results,one can design and synthesize hydroxytelechelic PLLGA and PCG copolymers and corresponding shape memory multiblock copolymers with desired transition temperatures.
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发布时间：2021-03-19
Research Bulletin
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