最新刊期
卷 ， 期 5 ， 2011
- 摘要：A novel poly(Schiff base) containing 1,10-phenanthroline (DAPcPYA) was synthesized by the polycondensation of 2,6-pyridinedicarboxaldehyde (PYA) with 5,6-diamine-1,10-phenanthroline (DAP). Three polymeric complexes were first prepared by the reaction of polymer (DAPcPYA) with NiSO4, FeSO4,and NdCl3, respectively. The structures of the polymer and the complexes were characterized by IR, 1HNMR, and elemental analysis. The magnetic behaviors of these complexes were measured as a function of magnetic field strength (0~4.0106 A/m) at 5 K and as a function of temperature (5~300 K) at a magnetic field strength of 2.4106 A/m. The results show that DAPcPYA-Ni2+ and DAPcPYA-Nd3+ were soft ferromagnets, whereas DAPcPYA-Fe2+ exhibited the features of an antiferromagnet.
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发布时间：2021-03-19 - 摘要：The direct electrochemical copolymerization of pyrrole and caprolactam on an Indium-tin oxide (ITO) electrode was carried out by potentiostatic methods. The polymerization reaction was controled under the applied potential over 1.2 V vs. Ag/AgCl (saturated KCl) electrode in the nitromethane solution containing 0.05 M tetrabutyl ammonium tetrafluoroborate (Bu4NBF4), 0.1 M pyrrole and 1.5 M caprolactam. The composition of polypyrrole and polycaprolactam chain in the obtained products can be adjusted by controling the synthesis potential in the process of polymerization. Characterizations in the structure, morphology, and thermal properties of the novel copolymer were based on scanning electron microscopy (SEM), thermal gravimetrical analysis (TGA), Fourier transform infrared (FT-IR) spectra studies. The results showed that the electrochemical oxidation of pyrrole and caprolactam comonomers generates true copolymers rather than blends of the two homopolymers. The copolymer of pyrrole and caprolactam showed a better flexibility than pure polypyrrole obtained under the same polymerization condition. A probable mechanism of the copolymerization of pyrrole and caprolactam was proposed. The existence of polycaprolactam matrix in copolymer was desired to improve the hydrophilic characteristic and the biocompatibility of polymer film, and thus the copolymer film can be used for a good immobilization material of protein in the construction of electrochemical biosensors.
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发布时间：2021-03-19 - 摘要：With the purpose to decrease the crystallinity of poly(-caprolactone) (PCL), a small amount (8.5 mol%) of 2,2-dimethyltrimethylene carbonate (DTC) was added to copolymerize with -caprolactone (CL) using lanthanum tris(2,6-di-tert-butyl-4-methylphenolate) (La(OAr)3) as catalyst. The produced polyester P(CL-co-DTC) (PCD) was wellcharacterized by 1H-NMR, SEC, DSC and WAXS. The results showed random copolymer PCD was synthesized. DSC and WAXS results proved PCD had a much lower crystallinity (c = 28.1%) compared to that of PCL (c = 44.7%). PCD, as well as PCL homopolymer containing 8 wt% salicylic acid as a model drug was electrospun into ultrafine fibers with the diameter around 1 m and further submitted to in vitro drug release test. The results showed that the PCD electrospun mat exhibited a controlled drugrelease behavior while the PCL one displayed a burstrelease behavior. The DSC and WAXS results showed PCL electrospun fibers had a much higher crystallinity (c = 79.3%) than that of PCD electrospun fibers (c = 40.3%) and this explained the difference of drugrelease behaviors of the two electrospun mats. It was the non-crystalline domains involved in PCD that facilitated the compatibility between the polymer matrix and salicylic acid and allowed the drug to be released in a controlled way through the thermal motion of the polymer chain. This study provided a strategy for a better drug inclusion and release behavior by lowering the crystallinity of matrix material.
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发布时间：2021-03-19 - 摘要：Novel ABC triblock copolymers of poly(methyl methacrylate)-b-poly(n-butyl methacrylate)(or n-octadecyl methacrylate)-b-poly(2-perfluorooctylethyl methacrylate) (PMMA230-b-PBMA12 (or PODMA12)-b-PFMAn) were synthesized by atom transfer radical polymerization(ATRP).The effect of selective solvents on surface structure of the triblock copolymers film was investigated by X-ray photoelectron spectroscopy (XPS),X-ray diffraction (XRD) and dynamic light scattering (DLS).The higher surface enrichment of fluorinated moieties in PMMA230-b-PBMA12-b-PFMA1 was found as the film was cast by cyclohexanone solution,compared to the film cast by toluene solution.When the length of PFMA units was about 4,the ratio of fluorine to carbon was nearly the same.As for PMMA230-b-PODMA12-b-PFMAn,the fluorinated moieties can segregate more easily on the surface as the film was cast with toluene solution,compared to the film cast from cyclohexanone solution.The reason could be attributed to the difference in compatibility between solvent and the middle block in triblock copolymers,which would affect the stability of triblock copolymers micelle in various solutions.When the solvent was the good solubility for the middle block chain,there were unstable and loose packed micellar aggregates in solution.The unstable micelle of the triblock copolymer in solution was in favor of fluorine segregation on the surface during film-formation.During film formation,the perfluoroalkyl side chains can easily segregate to the surface and be packed in a well-ordered manner,resulting in enhanced surface enrichment of fluorine element.The results suggest that copolymer solution properties, may play an important role in structure formation on the solid surface,in addition to for the molecular chain structures of copolymers.
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发布时间：2021-03-19 - 摘要：Graft copolymers of high vinyl polybutadiene with butadiene-styrene copolymer (SB-grafted HVPBR) were synthesized by polymerization of butadiene in hydrogasoline solution of styrenebutadiene random copolymer (SB) (St% was 30%,Mn was 3.710-3) using a homogeneous MoCl3(OC8H16)2/Al((OPhCH3)(i-Bu)2 catalyst.Graft copolymers were formed when the growing polybutadiene chains threaded through the double bonds of the dissolved SB,giving copolymers with proliferating chain structures.SB was synthesized by anionic polymerization with butyl-lithium as initiator and tetrahydrofuran as structural regulator.The effect of addition amount of SB on the structure and properties of SB-grafted HVPBR was studied by means of FTIR,GPC and GPC-MALLS-Viscometer Analysis System etc.Compared with HVPBR,the molecular weight of SB\|grafted HVPBR and molecular weight distribution and the content of gel raised slightly.The solution dynamic viscosity of HVPBR was decreased to a great extent as a result of the presence of the SB graft chain.The graft efficiency was the highest when the SBs addtion was 3 wt%.Glass transition temperature (Tg) of SB-grafted HVPBR/SBR compounds at varying blending ratios were measured using differential scanning calorimetry (DSC).The results of DSC confirmed that the compatibility of HVPBR and SBR was improved effectively by grafting SB onto HVPBR.
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发布时间：2021-03-19 - 摘要：The third component of 5-sulfoisophthalic acid dihydroxy propyl ester sodium salt (SIPP) and the fourth component of poly(butylene adipate) (PBA) or polyethylene glycol (PEG) were added respectively in the process of esterification and polycondensation for the polymerization of 1,3-propanediol (or trimethylene glycol) and terephthalic acid.Three kinds of cationic dyeable poly(trimethylene terephtalate) copolyesters (PTTs) were synthesized by direct esterification-polycondensation process,and were characterized by differential scanning calorimetry (DSC),1H-nuclear magnetic resonance (1H-NMR) and thermogravimetric analysis (TGA),respectively.Compared to PTT,the thermal degradation properties for PTTs modified by SIPP,PBA and PEG almost kept invariant.DSC was used to further investigate the nonisothermal crystallization properties of PTT and the cationic dyeable PTTs,and the experimental results indicated that the Avrami exponents for PTT were from 4.24 to 4.50,suggesting that nonisothermal crystallization mechanism for PTT was simultaneously controlled by homogeneous and heterogeneous nucleation,and the nonisothermal crystallization for PTT was very complex.The Avrami exponents for PTTs modified by SIPP,PBA and PEG were from 1.72 to 2.64,and it was assumed that the nonisothermal crystallization mechanism for cationic dyeable PTTs was the heterogeneous nucleation.The crystallization activation energy of cationic dyeable PTTs was higher than that of PTT,suggesting that the crystallization was more sensitive to the temperature.Therefore,it was of great importance to control the temperature in spinning process.
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发布时间：2021-03-19 - 摘要：Four Lanthanum Schiff－base complexes were synthesized, and the polymerizations of alkyl isocyanates were studied using these complexes as single component catalysts. Lanthanum Schiffbase complexes La(HSalen1~4)3 have been synthesized by metathesis reaction of anhydrous LaCl3 with Schiffbase sodium salts NaSalen. The complex La(HSalen2)3 with the formula of ［3,5－tBu2－2－(O)C6H2CHNC6H5］3La(THF) was characterized by Xray diffraction, and the structure around Lanthanum center could be described as a pentagonal bipyramid. The polymerization of alkyl isocyanates was successfully carried out by using these complexes as single component catalysts, and the ［OC6H2CHNC6H5］3La(THF) complex (La(HSalen1)3) shows the highest catalytic activity to the polymerization of isocyanates. The influences of polymerization temperature, polymerization time, the concentration of catalyst and monomer, and the polymerization solvent on the polymerization of hexyl isocyanate (HIC) catalyzed by La(HSalen1)3 were investigated. It was found that under the polymerization conditions examined, PHIC can be prepared under -40℃~20℃ with complex La(HSalen1)3 as catalyst. Due to the depolymerization, higher reaction temperature leads to low polymer yield and molecular weight of PHIC obtained. Confirmed by GPC analysis, prolonging polymerization time is also in favor of depolymerization, the GPC profile of PHIC prepared after 12 h polymerization indicates the exist of dimmers and trimers. PHIC could be prepared with yield of 75.5%, numberaverage molecular weight (Mn) of 6.00104and MWD of 3.86 under the following optimum conditions: ［HIC］= 3.43 mol/L, ［La(HSalen1)3］= 8.5810-3mol/L, polymerization at -40℃ for 12 h in toluene.
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发布时间：2021-03-19 - 摘要：In this work,long chain branched (LCB) polypropylene (PP) was prepared by multimonomer melt grafting with the presence of 1,6hexanediol diacrylate (HDDA) and styrene (St) in a Haake Rheomix batch mixer.FTIR spectra showed the addition of St to the melt grafting system could significantly promote the graft degree of HDDA onto PP backbones.For fixed initiator and HDDA monomer content,the more the addition of St monomer,the higher the graft degree of HDDA monomer was.Investigations on the rheological properties of grafted PP indicated the existence of LCB structures.During melt grafting,the graft degree of HDDA monomer increased,melt flow rate (MFR) of the grafted PP decreased and more LCB PP was generated with increasing the St monomer concentration.Derivative thermogravimetry (DTG) measurements showed that the thermal stabilities of the grafted PP were greatly enhanced,which was much better than iPP.The decomposition temperatures,known as T5% and Tmax,were more than 46 K higher than iPP,and more than 30 K higher than grafted PP without St,implying the thermal stabilities of the grafted PP were greatly enhanced by multimonomer melt grafting with St and HDDA monomers.Xray diffraction (XRD) results demonstrated the graft processing by multi-monomer melt grafting could well induce the crystallization of PP form crystals.Differential scanning calorimetry (DSC) characterization showed that grafted PP had higher crystallization temperature and wider melting and crystallization peaks,due to the heterogeneous nucleation effect and restriction of the existence of grafted PP chains,respectively.
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发布时间：2021-03-19 - 摘要：Spherulitic morphologies of a series of linear poly(Llactide)s (PLLA),which was synthesized by ring opening polymerization (ROP) using initiators with different structures,i.e.the incoming end groups,were observed through direct meltcrystallization process by polarized optical microscopy (POM).It has been verified that the flexibility of the end group has a significant influence on the banded structure of PLLA spherulites.It was found that the spherulitic band spacing periodicity of PLLA initiated by rigid benzyl alcohol (BPLLA) was much smaller than that of PLLA initiated by flexible lauryl amine (L-PLLA) with similar molecular weight at certain crystallization temperature.However,this end group effect was decreasing with increasing molecular weight.For B-PLLAs,the band spacing periodicity of spherulites increased with molecular weight increasing noticeably,for example,B-PLLA1 having a molecular weight of about 1700 yielded spherulites with band spacing periodicity being only several micrometers and spherulites of B-PLLA4 having a molecular weight of about 7000 had the band spacing periodicity more than 150 micrometers.Meanwhile,the temperature windows for the formation of regular banded spherulites of B-PLLAs shifted to higher region and became narrower with increasing molecular weight.Finally,a model was suggested to illustrate the effects of end group and molecular weight on the formation of twisting PLLA lamellae.
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发布时间：2021-03-19 - 摘要：The monomer (DHEMA(G1)) was synthesized by esterification of the 2-hydroxyethyl methacrylate with acetonide protected 2,2-bis(methylol)propionic acid,and then undergone the ATRP to give the macroinitiator PDHEMA(G1)-Br.By using PDHEMA(G1)-Br to initiate styrene,PDHEMA(G1)-b-PS block copolymer was prepared.Based on the PDHEMA(G1)-b-PS as reactive precursor,through iterative process of the deprotection of acetonide and dendronization by esterification with bis-MPA anhydride,the dendronized-linear amphiphilic block copolymers PDHEMA(Gn-OH)-b-PS(n=2~3) were prepared,and the asymmetrical structure of designed copolymers was a combination of a hydrophilic multihydroxyl dendronized PDHEMA(Gn-OH) block and a hydrophobic linear PS block.The resultant copolymers were characterized by IR and 1H-NMR.The self-assembly morphology of PDHEMA(Gn-OH)-b-PS(n=1~3) in the binary solvent mixture (DMF/CH3OH) was investigated with the copolymer concentration at 2 mg/mL.When the CH3OH content was at 50 wt%,PDHEMA(G1-OH)-b-PS,PDHEMA(G2-OH)-b-PS and PDHEMA(G3-OH)-b-PS self-assembled into spherical micelles with core-fringe structure.The diameter of micelles increased with increasing generation of dendronized blocks.For the copolymer PDHEMA(G3-OH)-b-PS,when the CH3OH content was at 66 wt%,the compound rodlike micelles containing branch and ring structure were formed and spherical micelles were also encountered occasionally.When the CH3OH content reached 75 wt%,only the compound rodlike micelles contaning branch and ring structure were observed.The unique morphological variety of muti-rings could be attributed to the coexistent effect of branch and ring during the development of rodlike micelles.
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发布时间：2021-03-19 - 摘要：As a microreactor,hollow microspheres could be used to load magnetic nanoparticles.Asymmetric hollow polymeric microspheres with micropores of 14.9 nm,alkyl bromine groups on exterior wall and carboxyl groups on interior wall were produced through three steps: (a) synthesis of the coreshell microparticles with copolymer of maleic anhydride (MAn) and divinyl benzene (DVB) as the shell,and copolymer of maleic anhydride (MAn) and vinylacetate (VAc) as the core; (b) surface bromizing of the coreshell microparticles by reaction with dibromoethane; (c) etching of the cores with acetone,and followed by the hydrolyzing of the anhydride groups on interior wall.Fe3O4 magnetic nanoparticles were loaded into the cavity of prepared hollow polymeric microspheres by two steps: first,Fe2+ and Fe3+ were infiltrated into the hollow microspheres and selective adsorbed on the interior wall under the effect of carboxyl groups; secondly,in appropriate condition,coprecipitation were carried out to obtain Fe3O4 magnetic nanoparticles.In addition,influences of parameters relating to the above mentioned reaction,such as the mole ratio of Fe2+ and Fe3+,reaction temperature and reaction time,on the saturation magnetization of the magnetic microspheres were investigated.The results show that,the optimum reaction conditions to the balance of loading selectivity and value of saturation magnetization were as follow: molar ratio of Fe2+ and Fe3+ was 2/3,reaction temperature was 80℃ and reaction time was 1.5 h,for obtained the best value of saturation magnetization 12.34 emu/g.
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发布时间：2021-03-19 - 摘要：A novel and facile method using a printed gradation photomask combined with photoreactions for preparing polymer surfaces with gradient distribution of surface energy, grafting layer thickness and grafting chain density was developed. The gradation photomask with gradient change of photo transmittance intensity, almost in the range of 0~100% at both 254 nm and 365 nm, has been successfully prepared by direct printing black ink onto the biaxially oriented polypropylene and silica (BOPP/SiOx) hybrid film. The applications of the gradient photomask in photoinduced reactions, such as confined photocatalytic oxidation (CPO) and photografting polymerizations, have been exploited. In CPO reaction with a printed gradient photomask, the static water contact angles (CAs) of modified surfaces of BOPP and PET films exhibited the surface energy gradient properties, for example, the CAs of BOPP decreased almost linearly from about 103 (unmodified) to about 39 and PET film from about 78 (unmodified) to less than 10 respectively. In UV induced surface grafting polymerization of acrylic acid (AA), the dry thickness of PAA brushes showed a gradient change from about several nanometers to bout 750 nm on the BOPP film substrate. While in precipitationphotografting polymerization of acrylamide (AM), ATR-FTIR, X-ray photoelectron spectroscopy (XPS), fluorescence microscopy and scanning electron microscopy (SEM) demonstrated the existence of the gradient grafting chain density on the polymer surfaces, i.e, the content of Nitrogen determined by XPS increased from about 0 wt% of pristine BOPP film to about 1128%. So far, this is one of the most convenient methods reported for preparation of polymer gradient surfaces, and it is a versatile facile method in preparation of a gradient surface controlled by the gradation photomask.
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发布时间：2021-03-19 - 摘要：In order to improve the performance of poly(butylenes succinate) (PBS) like the crystallinity and mechanical properties,PBS/nano kaolin blends were prepared by mechanical melting mixing.The microstructure,crystallinity,mechanical properties and dispersion of the PBS/nano kaolin were studied respectively with infrared spectrometer (FTIR),differential scanning calorimeter (DSC),universal material testing machine and scanning electron microscope (SEM).Infrared spectra showed picture shown that the modifier could be bonded to nano kaolin.The DSC results indicated that the onset (denoted as To ,c),peak (denoted as Tp ,c) and end crystallization temperature (denoted as Te ,c) of PBS were increased respectively.DSC melting curves for the meltcrystallized samples were obtained at 10 K min-1.Double endothermic peaks,a hightemperature peak H and a lowtemperature peak L,and an exothermic peak located between them appeared.At the same time,the crystallization degree rose first and declined finally as the nano kaolin content increased.When the content of nano kaolin was decreased,the notched impact strength,elongation at break and tensile strength of PBS/nano kaolin blends were improved obviously.The SEM results showed that at low contents nano kaolin was dispersed evenly in the blends,while agglomeration of nano kaolin was observed in blends with increasing kaolin content.The improving of the mechanical performance of PBS/nano kaolin blends is correlated with the variation of nano kaolin content.
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发布时间：2021-03-19 - 摘要：The unique rheological behavior of carboxylterminated polybutadiene (CTPB)/organoclay nanocomposite gels was studied under steady shear on a HAAKE RheoStress 600 instrument.The microstructure of nanocomposite gels was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM).The experimental results show that both irreversible and reversible viscosity transitions were observed in the temperature range from 26℃ to 116℃ in steady shear experiments on as-prepared samples.The irreversible viscosity transition is attributed to the exfoliation of the clay sheets,and the reversible viscosity transition can be understood as a shear-induced orientation-disorientation transition of the clay sheets.Moreover,the in-situ dispersion process of organoclay in CTPB matrix was observed by rheological experiments,and three important factors that significantly affected the rheological behavior of CTPB/organoclay nanocomposite gels in the steady shear measurement were studied:the temperature effect,the shear-induced orientation effect and temperature-sensitive polymer-clay interaction.Finally,a possible mechanism was suggested on the basis of the clay exfoliation and orientation-disorientation transition,and the mechanism was used to explain the effect of organoclay on the rheological behavior of CTPB gels and the relationship between the observed unique rheological behavior and the microstructure of nanocomposite gels.
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发布时间：2021-03-19 - 摘要：A coarsegrained model for symmetric ternary blends was constructed based on an experimental system of polyethylene/polyethylene oxide/polyethylenepoly(ethylene oxide)(PE/PEO/PEPEO) used in Batess work,and dissipative particle dynamics (DPD) method was employed to study the phase behavior of such ternary blends.Density distribution,order parameter and structure factor were used to characterize the phase and phase transition.The results show that the phase changes from lamellar (LAM) to bicontinuous microemulsion (BME) and then to macroscopic phase separation (PS) as the volume fraction of homopolymers H is increased.The phase sequences and their locations are in accordance with the experimental results.Especially,the BME region is located near the theoretical Lifshitz point.The LAM spacing increases with increasing H in LAM region and the interfacial tension decreases with increasing volume fraction of diblock copolymer (1-H) in PS region.Diblock copolymer molecules are disordered at interfaces due to the nature of curved interfaces in BME phase.The calculated structure factor on the BME structure is qualitatively in agreement with the TeubnerStrey static scattering model of microemulsion.In addition,the interfacial tension should reduce to a very low value in order to form stable BME structure.
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发布时间：2021-03-19 - 摘要：Poly(Nisopropylacrylamide) (PNIPAAm) brush surfaces were prepared via surface initiated atom transfer radical polymerization (SIATRP) on initiatorimmobilized silicon surfaces.The interactions between the PNIPAAm modified surfaces and plasma proteins in single protein solutions and in human blood plasma were investigated by radiolabeling and immunoblotting methods.The PNIPAAm modified surfaces showed much lower fibrinogen adsorption than the unmodified silicon.In particular,the adsorption of fibrinogen from plasma at either room temperature or body temperature was less than 5 ng/cm2,suggesting that these surfaces may possess good blood compatibility.In the plasma experiments the Vroman effect (high fibrinogen adsorption at short time or low plasma concentration) was not observed on the PNIPAAm modified surfaces,indicating good fibrinogen resistance in the early stages of blood contact.Moreover,the immunoblot data showed that adsorption from plasma of most of the proteins tested (including the contact coagulation factors:factor XII,factor XI,prekallikrein and high molecular weight kininogen) to the PNIPAAm modified surfaces was also significantly reduced.In general,our results suggest that PNIPAAm,used as a traditional thermoresponsive polymer,is resistant to nonspecific protein adsorption and may be a promising candidate for use in blood contact devices.
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发布时间：2021-03-19 - 摘要：The surface of ultrahigh molecular weight polyethylene (UHMWPE) was modified by direct fluorination.The shear strength of laminar UHMWPE bonded with epoxy resin was enhanced up to 4.72 MPa,which showed that the adhesive ability of UHMWPE was obviously improved.At the same time,this kind of adhesive ability remained at room temperature beyond one month.According to the results of scanning electron microscopy (SEM),the surface topography of UHMWPE did not change much after fluorination,which indicated that the improvement of adhesive properties did not depend on the surface roughness.However,the polarity portion of UHMWPE surface apparently improved and the surface energy increased from 30 mN/m to 42.47 mN/m from contact angle measurements.In addition,Xray photoelectron spectroscopy (XPS) and ATRinfrared spectroscopic analysis indicated that three kinds of polar functional groups,CF,COOH and OH,were introduced into the surface macromolecular chains in the form of covalent bonds,respectively.Thus,the bonding property of UHMWPE was improved owing to the change of surface chemical structure.Additionally,the mechanism of the formation of surface active groups by direct fluorination was proposed.
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发布时间：2021-03-19 - 摘要：By using dynamical method based on the TDGL (time dependent GinzburgLandau) equation with the rebuilded LaplaceBeltrami operator in a spherical shell, the phase behaviors of linear AB diblock copolymer melt confined in the closed spherical shells have been studied.Our approach has focused on the effects of the shells' radius and thickness on the morphology.By analyzing the microscopic phase patterns and the distribution of the components in the shells, we found that with the increasing of the radius and the thickness of the spherical shell, the confinement that polymer chains suffered was reduced and the macroscopic order of morphologies was gradually lost.Especially with the variation of shell thickness, the significant changes of component distribution of two asymmetric blocks within the shell were observed.
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发布时间：2021-03-19 - 摘要：Based on lattice model Monte Carlo simulations were carried out to investigate the influence of channel confinement on the properties of entangled (Linear250) and disentangled (Linear30) linear polymers with different sizes of channel.It is found that the molecular size of both Linear30 and Linear250 monotonously decreases with decreasing the channel size,i.e.channel confinement has similar influence on the static properties of linear chains whether they are entangled or not.As for the dynamical properties,the diffusion coefficient of Linear30 decreases with decreasing channel size; while that of Linear250 first increases and then decreases,which implies that the confinement will help to untangle the linear chains.Furthermore,the single target ring (which can be regarded as a test chain) in the matrix of confined Linear30 and Linear250 systems is also studied.The static properties of the target ring do not show clear change for these two systems; however,the diffusion coefficients of Z direction of ring in the entangled linear matrix show great difference from that of the disentangled one.This is a further evidence for the untangle effect of confinement.
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发布时间：2021-03-19 - 摘要：A novel series of soluble and curable phthalonitrileterminated oligo(phthalazinone imide)s with well controlled molecular weights were prepared by varying the molar ratio of dianhydrides to diamines.FTIR,1H-NMR and elemental analysis were applied to confirm the structures of the oligomers whose molecular weights were determined by 1H-NMR analysis.The crosslinking reactions of the phthalonitrile-terminated oligomers were performed under normal pressure in the presence of 4,4-diaminodiphenylsulfone as catalyst at elevated temperatures to form the s-triazine rings-containing thermosetting oligo(phthalazinone imide)s.The oligomers possess good solubility in common aprotic solvents such as chloroform,pyridine,mcresol and N-methyl-2-pyrrolidone due to the incorporation of crank,twisted and non-coplanar phthalazinone moiety into the polymer main chain,which disorders the close packing of the intermolecular chain.However,the cured samples are insoluble in all solvents because of the formation of the heterocyclic s-triazine networks during the crosslinking reaction of the cyano groups.The thermal properties of both the oligomers and the cured oligoimides were characterized by DSC,TGA and DTG.The oligomers have high glass transition temperatures(Tgs) in the range of 200~249℃.The cured samples show no Tg from 100~400℃ for the heterocyclic s-triazine networks decrease the flexibility of polymer backbone.And they exhibit excellent thermal stability with 5% weight loss temperature up to 522~532℃,10% weight loss temperature ranging from 556℃ to 567℃ and the carbonized residue values at 800℃ in the range of 69%~74%.For the excellent thermal stability of the cured oligoimides,they can be used as high performance polymeric materials in the aerospace and base materials for high temperature composite matrix.
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发布时间：2021-03-19
Research Article
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