SYNTHESIS AND CHARACTERIZATION OF POLY(L-GLUTAMIC ACID-co-L-ASPARTIC ACID)

Poly(amino acid)has been widely utilized in drug delivery,tissue engineering and biomedical materials.The biomaterials based on poly(glutamic acid)are usually modified via copolymerization with other monomers such as L-aspartic acid to improve the uncontrolled degradation rate.The ring-opening homo- and co-polymerization ofγ-benzyl-L-glutamate N-carboxyanhydride(BLG-NCA)andβ-benzyl-L-aspartate N-carboxyanhydride(BLA-NCA)were carried out in solution by using triethylamine(TEA)as initiator.The BLG-NCA homo...     

Thermosensitive polyion complex micelles prepared by self-assembly of two oppositely charged diblock copolymers

Polyion complex (PIC) micelles were spontaneously formed in aqueous solutions through electrostatic interaction between two oppositely charged block copolymers, poly(N-isopropylacrylamide)-b-poly(L-glutamic acid) and poly(N-isopropylacrylamide)-b-poly(L-lysine). Their controlled synthesis was achieved via the ring opening polymerization of N-carboxyanhydrides (NCA), ε-benzyloxycarbonyl-L-lysine (Lys(Z)-NCA) or γ-benzyl-L-glutamate (BLG-NCA) with amino-terminated poly(N-isopropylacrylamide) macroinitiator and the subsequent deprotection reaction. The formation of PIC micelles was confirmed by dynamic light scattering and transmission electron microscopy. Turbidimetric characterization suggested that the formed PIC micelles had a concentration-dependent thermosensitivity and their phase transition behaviors could be easily adjusted either by the block length of coplymers or the concentration of micelles.     

SYNTHESIS AND CHARACTERIZATION OF POLY(AMINO ACID-UREA)S COMPRISING NOVEL TRIBLOCK COPOLYMERS OF POLY(TETRAHYDROFURAN) AND POLY(γ-BENZYL L-GLUTAMATE)S

A kind of novel triblock copolymers of poly(γ-benzyl L-glutamate)-b-poly(tetrahydrofuran)-b-poly(γ-benzyl L-glutamate)s(PBLG-b-PTHF-b-PBLG)was synthesized by using bis(3-aminopropyl)terminated polytetrahydrofuran to initiate the ring-opening polymerization ofγ-benzyl L-glutamate N-carboxyanhydride(BLG-NCA).The corresponding multiblock poly(amino acid-urea)s were prepared in one-pot protocol from the chain extension of PBLG-b-PTHF-b-PBLG with MDI.The resulting triblock and multiblock copolymers were chara...     

生物相容性BAB型两亲嵌段共聚物的合成及其自组装

Lys(z)-NCA was synthesized in the presence of triphosgene, amphiphilic triblock copolymers poly(N^c-CBZ-Lysine)-PEG-poly(N^c-CBZ-Lysine) were synthesized in DMF using amino-end ended PEG as initiator with the mechanism of anion ring opening polymerization. The structures of block copolymers were characterized by IR, ^1H-NMR,GPC and DSC. The results showed triblock copolymers with expected structure and low polydispersity in molecular weight could be synthesized by this method. At the same time, the self-assembling behaviors of block copolymer were investigated by TEM. A novel helical aggregates were found to be formed in DMF. Because of biocompatibility of two components of block copolymers, these block copolymers have potential applications in the field of biomaterials.     

Synthesis and characterization of a novel amphiphilic biodegradable β-cyclodextrin/poly(γ-benzyl L-glutamate) copolymer

β-Cyclodextrin/poly(γ-benzyl L-glutamate) (β-CD-PBLG) copolymers were synthesized by ring-opening polymerization of N-carboxy-γ-benzyl L-glutamate anhydride (BLG-NCA) in N,N-dimethylformamide (DMF) initiated by mono-amino-β-cyclodex-trin(H2N-β-CD). The structures of the copolymers were confirmed by IR, 1H NMR and GPC. The fluorescence technique was used to determine the critical micelle concentrations (CMC) of copolymer miceU solution, the diameter and the distribution of micelles were characterized by DLS. The results showed that BLG-NCA could be initiated by H2N-β-CD to produce copolymer. The nano-micells were formed by these copolymers in water.     

Reactivity Ratios of Diethyldiallylammonium Chloride with Acrylamide or Acrylic Acid

The compositions of copolymers of diethyldiallylammonium chloride (DEDAAC) with acrylamide (AM), acrylic acid (AA) or sodium acrylic acid (NaAA) at low conversion were determined by elemental analysis, and the reactivity ratios of monomers in copolymerization were obtained by Kelen-Tudos method. The results showed that the reactivity ratios rDE and rAM are 0.31 and 5.27 for DEDAAC with AM, rDE and rAA are 0.28 and 5.15 for DEDAAC with AA, and rDE and rNaAA are 0.40 and 3.97 for DEDAAC with NaAA, respectively. The copolymerizations for DEDAAC with AM, AA or NaAA are non-ideal copolymerization and the products are random copolymers.     

In-chain functionalization through the combination of ring opening copolymerization and oxime “Click” reaction towards X-ray opaque polylactide copolymers

X-ray imaging functionalization of biodegradable polyesters is a great demand and challenge in biomedical applications.In this work,a strategy of in-chain functionalization through the combination of ring opening copolymerization and oxime "Click" postfunctionalization was developed towards X-ray opaque polylactide copolymers.A functionalized cyclic carbonate was first synthesized and used as comonomer of polylactide copolymers,which were subjected to postfunctionalization of oxime "Click" reaction towards iodinated polylactide copolymers.The chemical structure and physical properties of the target products were traced and confirmed.In vitro cytotoxicity evaluation with 3T3-Swiss albino by Alamar blue demonstrated a low cytotoxicity.The X-ray radiopacity was analyzed by Micro-CT and quantified by Hounsfield Units value,which could be tailorable by the feedstock.It is a promising X-ray visible implantable biomaterial in biomedical applications.     

SYNTHESIS OF POLY ( ETHER-URETHANE) CONTAINING PENDANT AMINO GROUP

This paper is concerned with the synthesis of poly (ether-urethane) with pendant amino groups. The copolyether produced by ring opening copolymerization of tetrahydrofuran and epibromohydrin was treated with sodium azide in dimethylformamide to form azido substituted copolyether. The poly (ether-urethane) made from it was subjected to reduction reaction to convert azido group to amino group. The stress-strain behavior and dynamic-mechanical properties of poly (ether-urethane) containing pendant amino groups were studied.     

Synthesis and characterization of biodegradable aliphatic polyesters using dibutylmagnesium as initiator

Aliphatic polyesters were synthesized via the ring opening polymerization of the corresponding lactones initiated with dibutylmagnesium both in bulk and in solution. The resulting polymers were characterized by 1H, 13C NMR, GPC and XRD. The results indicated that dibutylmagnesium is an effective initiator for the ring opening polymerization of lactones.     

In-situ copolymerization of aniline with alkyl amine by APS： Kinetics and application

The kinetic study of in-situ eopolymerization of aniline with o- and p-methylaniline by ammonium persulfate （APS） has been carried out. UV-vis spectroscopic method was used to investigate the course of copolymerization. Structural characterization was studied by PT-IR spectral analysis. The electronic spectra of the copolymers poly（aniline-co-p-toluidine） and poly（aniline-co-o- toluidine） show blue shift. The shift has been observed in the bands corresponding to π→π^＊ transition as well as in the exciton transition. The increase in absorbance recorded during the reaction for different concentration of aniline, o- and p-toluidine at various intervals of time of polymerization reaction indicates a growth in the polymer formation. The resulting first-order rate constant was used to calculate the rate of copolymer formation using the rate equation -d[A]/dt = kc^n.     

Polyglutamate copolymers as a tissue-engineering platform: Polymer scaffold modification through aminolysis of poly(γ-benzyl-l-glutamate-co-2,2,2-γ-trichlorethyl-l-glutamate)

Homopolymers of γ-benzyl-l-glutamate (BLG) and its copolymers with more reactive 2,2,2-γ-trichlorethyl-l-glutamate (TCEG), poly(γ-benzyl-l-glutamate-co-2,2,2-γ-trichlorethyl-l-glutamate) (poly(BLG-co-TCEG)), were synthesized by ring opening polymerization of respective N-carboxyanhydrides (NCA). The copolymerization parameters of N-carboxyanhydrides were determined according to the Fineman-Ross and Kelen-Tüdõs methods. To be studied as potential material for fabrication of tissue engineering scaffolds, polyglutamates were processed into solid films by casting from solution in dichloroethane as well as to fibres by solution-spinning method. The feasibility of functional modification of polyglutamate films and fibres through aminolysis of glutamate ester side chains with 2-aminoethanol or with a 2-aminoethanol/1,6-diaminohexane mixture under various conditions was studied. The progress and extent of polymer side chain modification and the resulting surface modification of PBLG or poly(BLG-co-TCEG) films and fibres were analyzed by following methods: (a) the conversion of aminolysis of BLG units alone was determined from the amount of released benzyl alcohol extracted into hexane and followed by HPLC analysis, (b) the conversion of aminolysis of TCEG units in poly(BLG-co-TCEG) was calculated from elemental analysis, (c) the depth and extend of films surface modification was evaluated from the change of ester-amide ratio at the surface, as obtained from ATR IR measurements and (d) the amount of reactive free amino groups, created by aminolysis with 1,6-diaminohexane, was quantified by reaction with 2,4,6-trinitrobenzenesulfonic acid (TNBS).     

Self-assembling of biocompatible BAB amphiphilic triblock copolymers PLL(Z)-PEG-PLL(Z) in aqueous medium

A novel biocompatible BAB amphiphilic triblock copolymers which consist of poly(ethylene glycol) (PEG) and poly(ε-benzyloxycarbonyl l-Lysine) (PLL(Z)) were synthesized by anion ring opening polymerization of N-carboxyanhydride of ε-benzyloxycarbonyl-l-Lysine (l-Lys(z)-NCA) using α-amino-ω-amino-poly(ethylene glycol) as initiator in DMF. The block copolymers were characterized by IR, ¹H-NMR, GPC, DSC. The results showed that the block copolymers were of narrow molecular distribution and well defined structure. The self-assembled behaviors of block copolymers in aqueous medium were investigated. The effects of various factors, such as cosolvents, initial concentration, temperature, annealing time and times of frozen-thaw cycle etc., on the aggregate morphologies were investigated by transmission electron microscopy (TEM). Different morphological aggregates such as sphere, rod and vesicle etc. could be obtained at controlled conditions, at the same time, a novel helical aggregate was observed. These regular nanometer structures have potential applications in biomedicine due to the biocompatibility of two blocks.     

Synthesis and characterization of poly(succinimide-co-6-aminocaproic acid) by acid-catalyzed polycondensation of L-aspartic acid and 6-aminocaproic acid

The polycondensation of L -aspartic acid ( ASP ) with 6-aminocaproic acid ( ACA ) using o-phosphoric acid produced poly(succinimide-co-6-aminocaproic acid). The yield of the MeOH-insoluble copolymer decreased from 99 to 52% and that of the MeOH-soluble one increased from 9 to 47%, with increasing molar ratio of ACA in the monomer feed. The compositions of the succinimide ( SCI ) unit in the MeOH -insoluble and -soluble copolymers tended to be higher than those of ASP in the monomer feed. The copolymers with the 35 mol % SCI units or above were soluble in DMSO , DMF , and conc- H₂SO₄ , but those with the 20 and 21 mol % SCI units were soluble only in conc-H₂SO₄. The melting temperature appeared for the copolymers with less than 76 mol % SCI units. Poly(succinimide-co-6-aminocaproic acid) was easily hydrolyzed to yield poly(aspartic acid-co-6-aminocaproic acid), and it exhibited biodegradability toward activated sludge. © 1997 John Wiley & Sons, Inc.     

Synthesis and characterization of poly(p-dioxanone)-based degradable copolymers with enhanced thermal and hydrolytic stabilities

Herein, we presented a novel biodegradable copolymer via the chain extending reaction of poly(p-dioxanone)-co-poly(2-(2-hydroxyethoxy) benzoate) (PPDO-co-PDHB) prepolymer with hexamethylene diisocyanate (HDI) as a chain extender. The structures and molecular weight of PPDO-co-PDHB prepolymer and PPDO-co-PDHB-PU chain-extended copolymer are characterized via hydrogen nuclear magnetic resonance spectroscopy (¹H NMR) and viscosity test. The relationship between the molecular structures and properties of the chain-extended copolymers is established. The PPDO-co-PDHB-PU copolymers possess a better thermal stability comparing with the PPDO homopolymer. The study of mechanical properties shows that the elongation-at-break of PPDO-co-PDHB-PU is much higher than that of PPDO. The investigation of hydrolytic degradation behaviors indicates the degradation rate of PPDO can be controlled by adjusting the PDHB compositions, and proves that chain-extended copolymers exhibit an excellent hydrolytic stability being better than that of PPDO.     

Synthesis and Characterization of Amphiphilic Poly(caprolactone) Star Block Copolymers

Summary: Novel, star‐shaped, amphiphilic block copolymers composed of fully degradable poly(caprolactone) were synthesized by sequential addition polymerization. In the first step, four‐arm macroinitiators were produced by ring‐opening polymerization of caprolactone by initiation with pentaerythritol. Then, block copolymers were synthesized by sequential addition of 4‐(2‐benzyloxyethyl)‐ε‐caprolactone to the four‐arm macroinitiators. Star‐shaped, amphiphilic block copolymers containing poly(caprolactone)‐block‐poly[4‐(2‐hydroxyethyl)caprolactone] segments were obtained by catalytic debenzylation.

Four‐arm amphiphilic polycaprolactone star block copolymer.     

Synthesis and characterization of novel vinyl copolymers containing N-vinylphthalimide: Comonomers reactivity ratios and thermal stability

N-Vinylphthalimide (NVPh) was copolymerized with p-methylstyrene (PMS), p-methoxystyrene (PMOS) and p-chlorostyrene (PClS) at 60 °C, with 2,2′-azo-bis-isobutyronitrile as an initiator. Copolymer composition was determined by elemental analysis in case of the N-vinylphthalimide and p-methylstyrene comonomer pair, whereas proton nuclear magnetic resonance was used for the analysis of the two other copolymers.The reactivity ratios for each comonomer pair were estimated by the classical Fineman-Ross and Kelen-Tüdõs linear techniques. These data showed that N-vinylphthalimide was less reactive in all the cases and that the comonomer distribution, that was basically random in the poly(N-vinylphthalimide-co-p-methylstyrene) and poly(N-vinylphthalimide-co-p-chlorostyrene) copolymers, was rather alternate in the third poly(N-vinylphthalimide-co-p-methoxystyrene) copolymer. The difference observed in the reactivity ratios was discussed in reference to the structure of the comonomer units and the parent radicals. The thermal properties of the copolymers and model homopolymers were investigated by differential scanning calorimetry and thermogravimetric analysis.     

Synthesis and Characterization of Novel Aliphatic Poly(carbonate‐ester)s with Functional Pendent Groups

Summary: A novel cyclic carbonate monomer 5‐methyl‐5‐(succinimide‐N‐oxycarbonyl)‐1,3‐dioxan‐2‐one (MSTC) was prepared. The copolymers of MSTC with caprolactone (CL) were further synthesized by ring‐opening copolymerization. The copolymers with amido‐amine pendent groups were obtained by aminolysis of poly(MSTC‐co‐CL) with ethylenediamine. These copolymers were characterized by IR, ¹H NMR, ¹³C NMR spectroscopies and GPC. The hydrophilicity and degradability of the copolymers with amido‐amine pendent groups were greatly improved in comparison with the PCL homopolymer.

Hydrophilicity of PCL (1), poly(MATC‐co‐CL) (16.5:83.5) (2), and poly(MATC‐co‐CL) (29.5:70.5) (3).     

Graft copolymerization of anhydro sugar derivatives from macromolecular halides

Cationic graft copolymerizations of bicyclic acetals, 1,6-anhydro-2,3,4-tri-O-benzyl-β-D -glucopyranose (LGTBE) and 1,6-anhydro-2,3,4-tri-O-methyl-β-D -glucopyranose (LGTME), were investigated with macromolecular carbenium ions formed from polymers that contain reactive halogens. Macromolecular complex catalysts formed from chlorosulfonated polyethylene or poly(isoprene-co-chloromethylstyrene) by the action of phosphorus pentafluoride yielded graft copolymers with low proportions (0.6–16%) of poly(LGTBE) or poly(LGTBE-co-epichlorohydrin) branchings. It was found that macromolecular complex catalysts formed from poly(styrene-co-fluoromethylstyrene) or poly(methyl methacrylate-co-fluoromethylstyrene) by the action of boron trifluoride etherate give graft copolymers with high proportions (up to 80%) of poly(LGTBE) or poly(LGTME) branchings. In addition, the model reactions for the graft copolymerization of LGTBE were examined with organic halide-PF₅, organic halide-AgPF₆, and organic fluoride-BF₃·OEt₂ catalytic systems, of which the last two indicate that the polymerization is effected by a carbenium ion mechanism.