最新刊期
卷 ， 期 6 ， 2011
- 摘要：Poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAM-co-AA)) microgel was synthesized by precipitation polymerization.Poly(N-isopropylacrylamide-co-3-acrylamidophenylboronic acid) (P(NIPAM-co-AAPBA)) microgel was obtained by the modification of P(NIPAM-co-AA) microgel with 3-aminophenylbornic acid under 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) catalysis.Almost complete conversion of the carboxylic groups in P(NIPAM-co-AA) microgel was confirmed by the disappearance of the peak at 1711 cm-1 in FTIR spectra.Both microgels are thermosensitive,however,the volume phase transition temperature of P(NIPAM-co-AAPBA) microgel is much lower than that of P(NIPAM-co-AA) microgel,as a result of the introduction of hydrophobic phenylboronic acid groups.The P(NIPAM-co-AAPBA) microgel exhibits good glucose-sensitivity,as its size increases with increasing glucose concentration.The increasing glucose concentration also results in a decrease in the turbidity of the microgel dispersion,which makes it possible to trace the kinetics of the glucose-induced swelling by turbidity.The kinetic curves were fitted with single-exponential function and the corresponding characteristic swelling times were obtained.The time required for the system to reach swelling equilibrium is on the magnitude of 102 s.The swelling rate increases with increasing glucose concentration.Compared with the macroscopic hydrogel with same composition,the glucose-induced swelling of P(NIPAM-co-AAPBA) microgel is much faster.However,compared with the swelling of PNIPAM microgels induced by temperature,the glucose-induced swelling is much slower.关键词：Microgel;Thermosensitive;Glucose-sensitive;Swelling kinetics
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发布时间：2021-03-19
Rapid Communications
- 摘要：Block copolymers can self-assemble into a variety of shaped nanoparticles and ordered nanomaterials either in solution or in bulk,which has great potential applications in areas of nanomaterial and nanotechnology.For further development of these areas,functionalization of the self-assembled nanoparticles was eagerly wanted.To mediate the structures,shapes and functions of these nanoparticles,well-defined functional block copolymers for self-assembly need to be synthesized with controlled polymerization.In this review,development on self-assembly of block copolymers is summarized based on related research progress in this group.Reactive block copolymers were synthesized by controlled radical polymerization first,then shaped core-shell polymer nanoparticles were prepared by self-assembly of reactive block copolymers either in solution or in bulk.After chemical or physical crosslinking,the morphologies of the nanoparticles can be fixed and then novel methods for preparation of core-shell polymer nanoparticless were obtained.关键词：Block copolymer;Core-shell nanoparticles;Self-assembly;ATRP;RAFT;Functional nanoobjects
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发布时间：2021-03-19
Feature Articles
- 摘要：Stretching orientation and strain-induced crystallization of rubber is widely recognized to play key role in the self-reinforcement of natural rubber and some synthetic rubbers (such as chloroprene rubber,butyl rubber and hydrogenated nitrile-butadiene rubber).Therefore,studying these phenomena and behavior has substantial significance for understanding the mechanism of the rubber reinforcing.In this review,various characterization methods concerning stretching orientation and strain-induced crystallization of polymer materials as well as principles,features and applicable scope of these methods were summarized and compared.Current progresses in the research about stretching orientation and strain-induced crystallization of nano-fillers (including carbon black,silica,nano clay and carbon nanotube) reinforced rubber composites as well as thermoplastic elastomers were surveyed.Finally,the future developing trend in this research field was prospected.关键词：Elastomer;Nano reinforcement;Stretching orientation;Strain-induced crystallization
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发布时间：2021-03-19
Reviews
- 摘要：A polysilane with zirconium was synthesized by electrochemical method,using methyltrichlorosilane,allylchloride ,Cyclopentadiene and Zirconium tetrachloride as monomers.The product was characterized by FTIR,UV,NMR and XRD.Its double-bond,elements content,molecular weight and molecular weight distribution were determined.The cross-linking and pyrolysis of it were studied.The results show that the product yield is 71.2%,the retaining ratio of double bonds is 10.8%,the Zr content is 4.11% and Molecular weight and molecular weight distribution are 3746 and 3.24. It can dissolve in toluene,THF,chloroform and other common organic solvents,and has excellent film-forming properties.The introduction of cyclopentadienyl and allyl makes its maximum absorption wavelength widen and have a high degree of red shift.Cyclopentadienyl and Zr form big bond in the electrosynthesis process,leading to support the formation of cross-linking system.Double bonds can play the role of self-crosslinking,eliminating the need for the use of cross-linking agent.The introduction of double bond and Zr in polysilane brings forth much higher mass retaining ratio and better ceramic yield.It can be used as ceramic precursor,pyrolysis products are mainly SiC and ZrC.In addition,there are excess Si and SiO2. It provides a new way for the synthesis of polysilanes with unsaturated functional groups and heterogeneous elements.关键词：Polysilane;Double bond;Zirconium;Electrochemical synthesis;Ceramic
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发布时间：2021-03-19 - 摘要：Bacterial cellulose/polyacrylamide composite hydrogel (BC/PAM) was prepared through free radical polymerization in which polyacrylamide (PAM) was introduced into the network of bacterial cellulose (BC).Structure and properties of composite hydrogels were studied through scanning electron microscopy (SEM),infrared spectrum (IR),thermal gravimetric analysis (TGA),X-ray diffraction (XRD) and mechanical testing.SEM images of freeze-dried composite gels showed that polyacrylamide dispersed uniformally inside the network of BC and also coated on the surface of BC microfibers,which avoided the aggregation of BC mircofibers because of hydrogen bond during the drying process.It was found that the rehydration capacity of composite gels had been greatly enhanced and the shrinking of hydrogels converted to isotropic compared with the anisotropy of pure BC.IR results indicated that hydrogen bond interation formed significantly between BC and PAM,by which stable networks of PAM and BC formed although the cross-linker wasnt used during the polymerization of AM.X-ray diffraction results showed that PAM had a certain impact on the orientation of crystal face (10) during the drying process.TG results showed that the thermal stability of the composite hydrogels significantly increased.The first decomposite temperature increased to 385℃ compare with 320℃ of pure BC.Compression testing results indicated that the mechanical properities increased greatly.The compression strength and modulus of BC/PAM composite hydrogels increased to 2350 kPa and 212 kPa compared with 130 kPa and 8.36 kPa of the pure BC,respectively.关键词：Bacterial cellulose;Polyacrylamide;Hydrogel;Compressive strength
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发布时间：2021-03-19 - 摘要：A kind of semi-rigid main-chain polyelectrolyte,poly(p-xylylene-4,4'-bipyridinium dibromide) (PXV) was synthesized by Menshutkin reaction,then a series of novel polyelectrolyte-surfactant (PXV-Cn) complexes were produced by electrostatic self-assembly through stoichiometric mixing of PXV with various anionic surfactants of sodium aliphatate (Cn-1COONa,n= 10,12,14,16,18).The supramolecular structure and mesomorphic phase behavior of thus assembled PXV-Cn complexes were preliminarily investigated by DSC,TGA,XRD,and FTIR.Based on the FTIR spectroscopic evidence,variant temperature XRD data and thermal analysis enthalpic quantitative calculation,a lamellar mesomorphic supramolecular structure was suggested with the polar head groups of the aliphatate surfactants and the polyelectrolyte PXV composing the polar layer while the alkyl side chains constructing the apolar layer.Furthermore,it was found that the alkyl side chains in the PXV-Cn complexes formed an end-to-end bilayer structure with about eight methylene groups near the head group in the amorphous state and others in the crystalline structure.Among them PXV-C10 with the shortest surfactant alkyl group only possessed the least ordered triclinic crystal phase T,while the most ordered hexagonal crystal H dominated in those complexes with n16,and variant crystalline polymorphs coexisted in those with intermediate n=12 or 14. The melting points Tm increased with increasing n,the complexes with longer alkyl chains of n16 exhibited almost reversible crystalline phase changes in the heating-cooling thermal cycles.This kind of polyviologen-surfactant complexes also showed better thermal stability without any remarkable weight loss below 200℃.The employment of the polyelectrolyte-polyviologen possessing redox properties made it a promising functional polyelectrolyte-surfactant complex for electrochromism and photochromism applications.关键词：Polyviologen;Sodium aliphatate;Polyelectrolyte-surfactant complex;Self-assembly;Phase behavior;Liquid crystal
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发布时间：2021-03-19 - 摘要：1,1-Bis(4-methoxyphenyl)ethylene (BMPE) was prepared from -ketocarboxylic acids and anisole,and with demethylation reaction a kind of biphenol 1,1-bis(4-hydroxyphenyl)ethylene (BHPE) containing crosslinkable moiety was obtained.The structure of the monomers was measured by 1H-NMR,elemental analysis,and the melting point of the monomers was measured by DSC.A kind of photo-crosslinkable fluorinated poly(arylene ether) has been prepared by polycondensation reaction with BHPE and decafluorobiphenyl (DFBP) by using suspending CaH2 with trace amount of KF as catalyst at low temperature.The structures of the obtained polymer were measured by 1H-NMR and 19F-NMR.The molecular weight of polymer was monitored by gel permeation chromatography (GPC),and the resulting number-average molecular weight is 23400 and the polydispersity index index is 2.94. The obtained polymer exhibits excellent solubility in common organic solvents at room temperature which makes it easy for optical film fabrication.The photo curing of the polymer was monitored by FTIR spectroscopy,and after UV irradiation 10 min the polymer can be completely crosslinked with the present photo initiator.The cured polymer shows good chemical resistance.So the polymer can be used for multi-layer processing.The obtained polymer also shows good thermal stability (the glass transition temperature is 160℃,the temperatures of 5% mass-loss is 465℃ after curing).关键词：Fluoropolymers;Poly(arylene ether);Photo curing
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发布时间：2021-03-19 - 摘要：A simple and attractive method for preparing bioactive surfaces which can effectively promote cell adhesion was introduced.Poly(N-methacryloyloxysuccinimide) (PNMASI) brushes containing a large amount of N-hydroxysuccinimide (NHS) active esters were prepared via surface initiated atom transfer radical polymerization (ATRP) on initiator-immobilized silicon surfaces.It was found that as the polymerization time increased,the thickness of PNMASI graft layer increased linearly,suggesting the controllability of the reaction.Protein adsorption test indicated that the PNMASI modified surfaces owned the great binding capacity of immobilized bioactive molecules.Furthermore,poly(oligo(ethylene glycol) methacrylate)-block-poly(N-methacryloyloxysuccinimide) (POEGMA-b-PNMASI) copolymer modified surfaces were synthesized via surface initiate consecutive ATRP.Then fibronectin,a typical extracellular matrix protein,was used as a model bioactive molecule and immobilized on the POEGMA-b-PNMASI modified surfaces via formation of covalent amide bonds between NHS active esters and the primary amide groups on fibronectin.The underlying POEGMA layer will not only resist non-specific protein adsorption,but also provide a hydrophilic surrounding microenvironment,which is helpful to maintain the bioactivity of immobilized fibronectin.The results of protein adsorption and cell adhesion characterizations indicated that these bioactive surfaces could improve cell adhesion and spread effectively and maintain non-specific protein repellent property.关键词：Poly(N-methacryloyloxysuccinimide);Atom transfer radical polymerization;Bioactive surface;Cell adhesion
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发布时间：2021-03-19 - 摘要：A novel and well-defined comb-copolymer,ethyl cellulose-graft-poly(-caprolactone) (EC-g-PCL) was synthesized via ring-opening polymerization (ROP) of -caprolactone (CL) with ethyl cellulose as the macroinitiator.The following coupling reaction of 1-pyrenebutyric acid with hydroxyl-terminated poly(-caprolactone) (PCL) was carried out in the presence of dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP).Pyrene-containing comb-copolymers (EC-g-PCL-Pyr) with different graft ratios of pyrene groups were obtained by adjusting the molar ratio of EC-g-PCL and pyrene.The structure of the resultant products was characterized by 1H-NMR and FTIR spectroscopy.Thermal properties and crystalline morphologies were established by differential scanning calorimetric analysis (DSC) and atomic force microscopy (AFM),respectively.Thermal analysis showed the melting temperature of EC-g-PCL-Pyr was lower than that of EC-g-PCL,because of the change of crystalline form which was demonstrated by AFM photos.Optical feature was determined by UV-Vis and fluorescence spectrometer.Fluorescence analysis indicated that the fluorescence intensity of EC-g-PCL-Pyr comb-copolymers changed with the increasing of the graft ratio of pyrene when the pyrene concentration of their CHCl3 solution was the same.This comb-copolymer could be used in biomedical applications such as fluorescent drug delivery and fluorescent probe.关键词：Ethyl cellulose;Poly(-caprolactone);Fluorescent polymer;Comb copolymer
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发布时间：2021-03-19 - 摘要：The biodegradation behaviors of poly(p-dioxanone)/organo-montmorillonite (PPDO/OMMT) nanocomposites were investigated in an aqueous medium with spores of selected culture microorganisms at 28℃ for 90 days.The degradation of samples was characterized by mass loss,intrinsic viscosity variation,pH value,DSC and SEM.The results showed that the biodegradation rates of nanocomposite increased with the increase of OMMT contents.After 90 days degradation,the weight losses of pure PPDO and PPDO/5% OMMT nanocomposite in the aqueous medium with and without spores of selected culture microorganisms were 17.9%,28.4%,and 12.9%,18.0%,respectively.The biodegradation of PPDO/OMMT was mainly related to the hydrolysis degradation and was improved by selected culture microorganisms.During 30 days of degradation,the intrinsic viscosity of PPDO/OMMT nanocomposites decreased significantly and their weight losses increased slowly as a consequence of the random break of ester bonds in PPDO long chains.As the biodegradation proceeds,many kinds of water-soluble products such as organic acids and oligomeric acids were produced.Therefore,the pH value of aqueous medium decreased and the weight losses increased obviously with the progress of biodegradation.The biodegradation of samples occurred preferentially in the amorphous areas,leading to the increase of crystallinity.As the biodegradation time increased,the crystalline regions were attacked,which caused the decrease of crystallinity.After biodegradation,the remarkable erosion was found on the surface of PPDO due to the bio-erosion of microorganism.However,no remarkable cracks emerged on the surface of PPDO/5% OMMT nanocomposite,which was assigned to the interaction and adhesion of PPDO and OMMT.关键词：Poly(p-dioxanone);Organo-montmorillonite;Biodegradation;Aqueous culture;Microorganism
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发布时间：2021-03-19 - 摘要：Water-soluble sulfonated carbon nanotubes were prepared by diazotization.On this basis,a series of sulfonated carbon nanotubes (1~2 nm,8 nm,10~20 nm,30~50 nm) modified polyaniline composites were synthesized successfully using in situ oxidative polymerization method.FTIR spectra shows that the intensity ratio of I1580/I1490 increases with the decrease of the diameters of CNTs.Simultaneously,it can be found from the UV-Vis spectra that the absorption peak around 800 nm of the composites blue-shifts compared to the polyaniline nanorods.Aforementioned results indicate that the presence of the - interaction between the PANI and the sulfonated carbon nanotubes,and the charge transfer composites are formed,which increase as the diameter of CNTs decreases.Field emission scanning electron microscope (FESEM) images show the PANI/sSWCNT composite displays the morphological structure of the bundle of nanotubes coated with PANI while the PANI/sMWCNT composites exhibit the morphology of single nanotube coated with PANI.And with the increase of the diameters of carbon nanotubes,the diameters of the PANI/sMWCNT composites thicken gradually.The cyclic voltammetry results demonstrate that the composites have higher specific capacitance (309~457 F/g) compared to the PANI nanorods (271 F/g),and the specific capacitance of the composites increases with decreasing the diameter of CNTs.Moreover,the composites also have outstanding fast charge/discharge performance as electrode materials in the application of supercapacitors.关键词：PANI nanorods;Sulfonated carbon nanotubes;Chemical oxidative polymerization;Supercapacitors
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发布时间：2021-03-19 - 摘要：A novel sheet micro-structure polypyrrole (PPy) was synthesized via a self-assembly method using the inclusion compound of -cyclodextrin (-CD) with 5-(acetylamino)-4-hydroxy-3-(phenylazo)-2,7-naphthalenedisulfonic acid (Acid Red G,ARG) as the dopant and FeCl3 as the oxidant.The structures and morphologies of the synthesized sheet PPy were characterized by scanning electron microscopy (SEM),X-ray diffraction (XRD) and Flourier-transform infrared (FTIR) spectroscopy.The results indicated that these sheet PPy doped with the inclusion compound of -cyclodextrin with ARG showed 1~10 m in width,10~20 m in length and the thickness was about 200 nm under no-stirring condition.At the same time,the influence of temperature,the concentrations of various reactants and reaction time on the morphology of the synthesized sheet PPy was investigated.Based on the research results,the optimized synthesis condition for the PPy tubules was obtained.The best conditions of forming PPy micro-sheet are as follows:the reaction temperature is 5℃,the concentrations of pyrrole,-cyclodextrin and ARG are 0.31 mol/L,0.067 mol/L and 0.067 mol/L,the reaction time is above 12 h.The formation mechanism of the sheet PPy was also discussed.Characterization results of PPy (the elements and contents,XRF) and the reaction intermediates revealed the formation mechanism of PPy micro-sheet is that the especial aggregation of the complexes of Fe2+ and -CD/ARG inclusion compounds was considered as the template in the synthesis process of the micro-sheet PPy.Because of the layer arrangement of -CD/ARG inclusion compounds,the SO3H groups of ARG molecules were arranged in one surface of the layer structure.Then this finally induced the polymerization reaction and continuous growth of pyrrole monomers on one surface of the aggregation of the complexes template.关键词：Polypyrrole (PPy);-Cyclodextrin (-CD);Inclusion compound;Micro-sheet
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发布时间：2021-03-19 - 摘要：A novel biodegradable PLGA/TiO2 organic-inorganic hybrid nano-material was prepared by the reaction between activated carboxyl-terminated PLGA,which was synthesized by PLGA and succinic anhydride with TEA as catalyzer,and amino-terminated TiO2 nano-particles which were modified by amino propyltriethoxysilane (KH550).The structure and morphology of the materials were characterized by Fourier transform infrared spectroscopy (FTIR),1H nuclear magnetic resonance (1H-NMR),thermogravimetic analysis (TGA),environmental scanning electron microscopy (ESEM) and transmission electron microscopy (TEM) methods.The results showed that the PLGA was grafted successfully on the surface of nano scale TiO2 particles with 14% average grafting; PLGA/TiO2 hybrid nano-material dispersed uniformly in BSA aqueous solution without obvious aggregation and showed a better adsorptivity (81.3%) to model drug BSA as compared with that(43.3%) of pure TiO2 nanoparticles.Different kinds of the nanopaticles containing proteins BSA (TiO2-BSA and PLGA/TiO2-BSA) were loaded into polymer microspheres with PLGA as carrier by the solid-in-oil-in-water emulsion method.The drug loading content,entrapment efficiency and drug release in vitro of different drug containing microspheres were tested.The results indicated that the microspheres of PTB/P showed smooth morphologies,high entrapment efficiency 96% and drug loading content 14.6% and decreased burst effect of drug,compared with TB/P microspheres.关键词：TiO2 nano-particles;PLGA;Organic-inorganic hybrid;Drug control release
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发布时间：2021-03-19 - 摘要：A method was presented for the preparation of raspberry-like organic-inorganic nanocomposite microspheres with polystyrene (PSt) as cores and nano-silica particles as shells through miniemulsion polymerization in the presence of aqueous nanosilica dispersions.A small amount of nonionic CA-897 (poly(oxyethylene) octyl phenylether,with 40 oxyethylene units) was used as surfactant and 1-vinylimidazole (1-VID) as auxiliary monomer.Composite microspheres were obtained via the acid-base interaction between silica particles and auxiliary monomer 1-VID.TEM indicated that the colloidally stable composite microspheres had typical raspberry-like morphology,indicating the acid-base interaction was strong enough for the formation of long-stable composite spheres.The average particle sizes and the final silica contents adsorbed on the composite microspheres could range from 140 nm to 180 nm and 19 wt% to 31 wt%,respectively,depending upon reaction conditions.The influences of some synthetic parameters,for instance,CA-897 concentration,ultrasonic frequency,ultrasonic time on the polymerization stability,diameters,silica contents and morphology of the composite microspheres were studied in detail.With the CA-897 amount increase,the average diameter of the composite microspheres tended to decrease and the silica contents adsorbed on the latexes surface increased.Ultrasonic frequency had obviously influence on the average diameter and the silica content of composite microspheres,but the effect of ultrasonic time was less.关键词：Raspberry-like;Miniemulsion polymerization;Aqueous silica sol;Organic-inorganic nanocomposite microsphere
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发布时间：2021-03-19 - 摘要：The crystallization behaviors of single 2-bromopropionyl end-capped poly(L-lactide) (PLLA-Br) were studied to investigate the end group effect during polymer crystallization.PLLA was first synthesized through ring opening polymerization (ROP) using benzyl alcohol as initiator.Then the free hydroxyl end group of PLLA was modified into big rigid 2-bromopropionyl group to obtain PLLA-Br.It was found that PLLA-Br with single 2-bromopropionyl end group possessed higher glass transition temperature than PLLA,indicating that the introduced 2-bromopropionyl end group restricted the chain mobility of PLLA.More interestingly,the 2-bromopropionyl end group greatly affected the crystallization process of PLLA.During non-isothermal crystallization process,the cold crystallization temperature of PLLA-Br was about 12℃ lower than that of PLLA; During isothermal crystallization process after quenching to room temperature,the number of simultaneously growing spherulites (per unit volume) was much higher in the PLLA-Br sample than in PLLA.These results could be attributed to the facilitated nucleation ability of PLLA-Br during cooling process after modification by 2-bromopropionyl end group.Moreover,during isothermal crystallization process directly from melt,both the temperature window for PLLA to form regular banded spherulites and maximum spherulite growing temperature shifted to higher temperature region after end capping,while crystalline structure was identical.This may provide a simple and effective method for PLLA modification to modulate its crystallizability.关键词：Poly(L-lactide);End group modification;Nucleation effect
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发布时间：2021-03-19 - 摘要：The macro-CTA (chain transfer agent) of poly(N,N'-dimethylacrylamide) (PDMAM) containing trithiocarbonate groups was prepared by reversible addition fragmentation chain transfer (RAFT) polymerization.And then it reacted with N-isopropyl acrylamide (NIPAM) and N,N'-methylene-bisacylamide (BIS) to prepare the PNIPAM-g-PDMAM comb hydrogels with different lengths and contents of the grafted chains at 20℃.The porous comb hydrogels were prepare by using poly(ethylene glycol) (PEG4000) as a pore-forming agent.The structure of the hydrogels was characterized by FTIR (Fourier transform infrared spectrometer) and SEM (scanning electron microscope).The photos of SEM indicated that comparing with conventional hydrogels,the porous comb dydrogles with loose structure had a distinctive porous characteristic.The mechanism of hydrogels synthesis and the effects of the grafted chains and porous structure on the properties of hydrogels were discussed.Experimental results showed that the grafted chains significantly affected the properties of nonporous hydrogels,including swelling ratio,deswelling rate and LCST (lower critical solution temperature).Though the deswelling rate decreased,the grafted chains had no effect on the swelling ratio of the porous comb hydrogels.The formation of a porous structure has been shown to effectively enhance the deswelling rate of PNIPAM hydrogels without grafting chains,but it didnt change the LCST.关键词：N-isopropyl acrylamide (NIPAM);Photopolymerization;Porous/comb hydrogels;Reversible addition fragmentation chain transfer (RAFT)
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发布时间：2021-03-19 - 摘要：Recent advances on targeted drug delivery systems which interact with intracellular components or events such as pH change have been an exciting focus for biomaterials scientists. In present work, poly(L-glutamic acid) peptide dendron was synthesized, and dopamine was immobilized on it as the ligand to substitute the oleic acid on the surface of hydrophobic Fe3O4 magnetic nanoparticles via ligand exchange. The anticancer drug doxorubicin (DOX) was conjugated to the peripheral functional groups of poly(L-glutamic acid) dendron with pH sensitive hydrazine linkers to construct magnetic drug loaded nanocarriers. The structure of the dendron ligand was determined by 1H-NMR and ESI-TOF-MS. The poly(L-glutamic acid) dendron modified magnetic nanoparticles were characterized by TEM, SEAD, DLS and FTIR. The results showed that the crystalline structure of the magnetic cores were not varied after the ligand exchange, the modified magnetic nanoparticles exhibited excellent aqueous dispersity and stability. The DOX loading of modified magnetic nanoparticles with the average size of ca.63 nm was 52.4 mgg-1. The release rate of DOX from the magnetic nanocarrier in the acid medium (pH=5.0) was dramatically higher than that in the physiological conditions (pH=7.4).The poly(L-glutamic acid) dendron modified magnetic nanoparticles showed excellent biocompatibility and low cytotoxicity in vitro, and the Fe3O4-G2(Glu)-DOX conjugate was efficient in inhibiting the proliferation of HeLa cells. Therefore, the pH sensitive peptide modified magnetic nanoparticle as a nanocarrier could be effectively utilized in drug delivery system.关键词：Poly(L-glutamic acid) peptide dendron;Fe3O4 magnetic nanoparticles;pH sensitive;Drug delivery system
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发布时间：2021-03-19 - 摘要：A novel terpolymer of carbon dioxide,propylene oxide (PO) and D,L-lactide (D,L-LA) was synthesized successfully at 70℃ in toluene by using a polymer-supported bimetallic complex (PBM) as a catalyst.The terpolymer prepared was characterized by FTIR,1H-NMR,13C-NMR and 1H-1H COSY spectrum measurements,which showed D,L-LA was ring-opened and inserted into the backbone of PO-CO2 with the fixed molar ratio of PO and D,L-LA as 5 ∶1. Furthermore,the expected reaction mechanism suggested the initiation of PO was more facile than that of CO2. Meanwhile,a new computational method called nonlinear approximation method was introduced in this work to analyse the thermal degradation kinetics.FWO and Tang methods as well as nonlinear approximation method were chosen to calculate the apparent activation energy.The results showed the accuracy of this new method was high and the average relative error was less than 6.5% due to its more scientific calculation process when Vyazovkin model free method was chosen as the standard method.During the whole degradation process,the apparent activation values ( Ea ) were between 66.6 kJmol-1 and 140.3 kJmol-1,indicating a better thermal stability related with the higher Ea as compared with that of PPC in the early decomposition stage.The results of non-isothermal degradation kinetics also suggested the whole pyrolysis of the terpolymer was a multi-step process due to variation of Ea .关键词：Polycarbonate;Carbon dioxide;Thermal degradation kinetics
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发布时间：2021-03-19 - 摘要：On the bases of the diffusion mechanism of small molecules in polymers,fine crosslinkable LDPE was prepared using a method of solid-liquid diffusion through which uniform blending additives with LDPE could be realized and small molecules such as antioxidants and crosslink agent could be diffused into interior section of LDPE pellets from their surface.The solid-liquid diffusion techniques were optimized through analyzing crosslinking enthalpy and specific absorption strength and examining diffusion rate of additives into LDPE under different diffusion conditions by using DSC and FTIR.The results show that time,temperature and molecular structure are the main factors affecting diffusion.It is found that crosslinking enthalpy seems to be the same for the core and shell of LDPE under the conditions of diffusion time being 14 h and temperature being 80C,or being 24 h and 60℃.These phenomena imply that dicumyl peroxide (DCP) has diffused into the interior part of the LDPE pellet; Moreover,content of dilauryl thiodipropionate (antioxidant DLTP) in core and shell of LDPE approaches equal after it diffuses at 80℃ for 24 h,while diffusion rate of n-octadecyl -(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (antioxidant 1076) is remarkably lower than that of DLTP under the same conditions.Furthermore,the content of antioxidant 1076 in core of LDPE is merely half of that in the shell.It is suggested that the reason for this is due to its larger volume than that of DLTP.关键词：Solid-liquid diffusion;Crosslinkable polyethylene;Antioxidants;Dicumyl peroxide (DCP)
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发布时间：2021-03-19
Research Article
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