聚己内酯－聚乙二醇嵌段共聚物Ⅱ．组成、结晶性同降解性间关系

采用ＤＳＣ法测定了新嵌段共聚物聚己内酯（ＰＣＬ）－聚乙二醇（ＰＥＧ）嵌段共聚物（ＰＣＥ）的结晶性，研究了共聚物的结晶性同组成及降解性的关系．结果表明随着共聚物中ＰＥＧ组分的含量和分子量增加，共聚物的结晶性下降，亲水性提高，降解速度加快．     

聚乙二醇改性聚乳酸的研究

将丙交酯（ＤＬ ＬＡ）与聚乙二醇（ＰＥＧ）共聚得到了一系列高分子量的共聚物．用ＩＲ、１Ｈ ＮＭＲ和ＤＭＡ对它的结构和粘弹性进行了表征，并测定了其力学性能，同时对材料在加工过程中特征粘度的变化也进行了研究．结果表明，ＰＥＧ与ＬＡ的共聚物是一种三嵌段结构ＨＯ ＰＬＡ ＰＥＧ ＰＬＡ ＯＨ．当ＰＥＧ含量增加时，强度下降，伸长率增加，共聚物逐渐由脆性向韧性转变，因此用ＰＥＧ改性的ＰＬＡ是一种综合性能可调控的生物降解材料     

乙交酯/丙交酯/己内酯三元共聚物的合成及表征

生物降解性高分子具有在生理条件下可以自行降解、最终被降解为单体或成为二氧化碳和水,从而或被机体吸收、或通过代谢途径排出体外的特性,已被广泛用作药物释放体系的载体、手术缝合线、外科手术及组织修复材料等各个方面,是当前生物医用高分子的一个重要分支．脂肪族聚酯由于具有良好生物相容性而成为最引人注意和有发展前途的一类生物降解性高分子,其中聚乙交酯（ＰＧＡ）、聚丙交酯（ＰＬＡ）及丙交酯／乙交酯共聚物（ＰＬＧＡ）是这一类聚酯中应用最为广泛的几种．Ｍｉｌｌｅｒ等［１］研究发现乙交酯（ＧＡ）和丙交酯（ＬＡ）共聚…     

聚己内酯－聚乙二醇嵌段共聚物Ⅱ．组成、结晶性同降解性间关系

采用ＤＣＳ法测定了新嵌段共聚物聚己内酯－聚乙二醇嵌段共聚物的结晶性，研究了共聚物的结晶性同组成及降解性的关系。结果表明随着共聚物中ＰＥＧ组分的含量和分子量增加，共聚物的结晶性下降，亲水性提高，降解速度加快。     

可生物降解的聚乳酸弹性体的合成与表征

本文将丙交酯（ＤＬ－ＬＡ）与聚乙二醇（ＰＥＧ）的预聚体用甲苯－二异氰酸酯８０（ＴＤＩ）扩链，得到了一系列的聚乳酸（聚醚）型聚氨酯（ＰＥＧ－ＰＬＡ／ＰＵ）弹性体。对预聚体和弹性体分别进行了ＩＲ、ＨＮＭＲ和ＤＭＡ表征，并测定了弹性体的力学性能。结果表明，ＬＡ与ＰＥＧ生成的预聚体是一种三嵌段结构：ＨＯ－ＰＬＡ－ＰＥＧ－ＰＬＡ－ＯＨ。随着ＰＥＧ含量的增加，弹性体的玻璃化温度下降；ＰＥＧ分子量增大时，弹性体     

侧链含炔丙基的PLGA-PEG-PLGA三嵌段共聚物的合成与表征

通过简单易行的技术路线合成了炔丙基化乙交酯单体,以1,4-二甲氨基吡啶为催化剂,亲水性和生物相容性良好的聚乙二醇为大分子引发剂,在较滥条件下引发炔丙基化乙交酯和丙交酯的开环共聚,制备了侧链含炔丙基的聚(乳酸-羟基乙酸)-聚乙二醇-聚(乳酸-羟基乙酸)(PLGA-PEG-PLGA)三嵌段共聚物,并对产物的组成与结构进行了表征.为生物孤犊触乳聚酯的分子修饰、生物相容性的提高探索一条简单而有效的途径     

生物降解高分子纳米球的制备

聚丙交酯;聚乙二醇;三嵌段共聚物;生物降解聚合物;生物降解高分子纳米球的制备     

载银离子PLGA-PEG-PLGA温度敏感水凝胶的制备及体外抗菌性能

利用聚乙二醇(PEG 1000)引发乙交酯和 D,L-丙交酯开环共聚合, 制备了聚丙交酯乙交酯(PLGA)三嵌段共聚物(PLGA-PEG-PLGA)温敏水凝胶材料; 利用核磁共振氢谱( ¹H NMR)确定了产物的结构及组成. 通过还原硝酸银的方法制备银纳米粒子(AgNPs), 并将其与PLGA-PEG-PLGA三嵌段共聚物水凝胶混合, 制得新型AgNPs/PLGA-PEG-PLGA复合水凝胶; 对该复合水凝胶的相关性能进行了表征. AgNPs/PLGA-PEG-PLGA复合水凝胶仍然具有温敏性能, 随着温度升高可发生溶胶-凝胶的相转变; 还可以持续释放银纳米粒子, 从而发挥抗菌性能. 体外细胞实验结果表明, AgNPs/PLGA-PEG-PLGA复合水凝胶具有良好的生物相容性, 未见明显细胞毒性, 是具有应用前景的新型复合水凝胶.     

乳酸、羟基乙酸均聚物及共聚物的合成与结构表征

本文以氯乙酸为原料制得了高纯度和高产率的乙交酯（ＧＡ），以乳酸为原料制得了丙交酯（ＬＡ），并以它们为单体制得了聚乙交酯（ＰＧＡ）、聚丙交酯（ＰＬＡ）及乙交酯（ＧＡ）和丙交酯（ＬＡ）不同配比的共聚物（ＰＧＬＡ）．用ＩＲ、ＮＭＲ、ＤＳＣ、ＴＧＡ、ＤＭＡ和Ｘ－射线衍射分析确定了该系列聚合物的结构与性质．用电导法测定了它们的降解速度，并将该系列聚合物埋入动物体内进行体内降解和病理学实验．     

乳酸,羟基乙酸盐聚物及其聚物的合成与结构表征

本文以氯乙酸为原料制得了高纯度和高产率的忆较酯（ＧＡ），以乳酸为原料制得了丙交酯（ＬＡ），并以它们为单制得了聚乙交酯（ＰＧＡ）、聚丙交酯（ＰＬＡ）及忆较酯（ＧＡ）和丙交酯（ＬＡ）不同配比的共聚物（ＰＧＬＡ）＞有ＩＲ；⑽ＭＲ、ＮＭＲ、ＤＭＡ和Ｘ－射线衍射分析确定了该系列聚合物的结构与性质。用电导法测定了它们的降解速度。并将该系列聚合物埋入动物体内进行体内降解和病理学实验。     

聚对二氧环己酮/聚乙二醇多嵌段共聚物的合成与表征

首先合成双端羟基的聚对二氧环己酮预聚物(PPDO)和双端羧基的聚乙二醇预聚物(PEG),然后以丁二酸酐/二环己基碳二亚胺(DCC)将PPDO与PEG偶联共聚,得到PPDO/PEG多嵌段共聚物.通过1H-NMR和GPC表征了聚合物的结构和分子量.采用差示扫描量热法(DSC)和热重分析(TGA)研究了共聚物的结晶性能和热稳定性.用透析法制备了共聚物纳米粒子,并用动态光散射(DLS)表征了共聚物纳米粒子的粒径及分散度,结果表明,随着共聚物亲水链段PEG含量的增加,其纳米粒子更易形成,粒子粒径随共聚物分子量增大而增大.     

Synthesis and characterization of (AB)n-type poly(l-lactide)-poly(dimethyl siloxane) multiblock copolymer and the effect of its macrodiol composition on urethane formation

An (AB)_n-type multiblock copolymer containing alternating poly(l-lactide) (PLLA) and poly(dimethyl siloxane) (PDMS) segments was synthesized by chain extension of hydroxyltelechelic PLLA-PDMS-PLLA triblock copolymers, which were prepared by the ring-opening polymerization of l-lactide initiated by α,ω-functionalized hydroxyl poly(dimethyl siloxane), using 1,6-hexamethylene diisocyanate as a chain extender. The triblock and the multiblock copolymers were characterized by FT-IR, ¹H NMR and GPC. From the results of thermal analysis, two glass transition temperatures which were measured by DSC showed the occurrence of phase separation phenomena in the triblock and multiblock copolymers because of the difference of solubility parameters between PLLA and PDMS segments. The effect of the chemical composition of the triblock copolymers, including the Mw and the constitutive segment chain length of the macrodiol, on the development of the Mw of the multiblock was discussed based on diffusion effect. Furthermore, the consumption of the isocyanate groups was determined by FT-IR to investigate the dependence of the reaction kinetics of the urethane formation on the chemical composition of the triblock copolymer. The results reveal that the order of the chain extension reaction depended on the Mw of the triblock copolymer: a second order reaction was transformed into a third reaction as the Mw of the triblock copolymer increased from 7000 to 25,000 (g/mol) perhaps because of the inhibition of the formation of an active complex involved in the catalyzed-urethane reaction by the polymer chain aggregation. Finally, the mechanical properties of the multiblock copolymers demonstrated that the introduction of the extremely flexible PDMS segment substantially improved the elongation at breakage, and the tensile strength and the tensile modulus declined due to the intrinsic elasticity of such segments.     

Crystallization behavior and biodegradation of poly(3-hydroxybutyrate) and poly(ethylene glycol) multiblock copolymers

Block copolymerization by using isocyanates is an effective method for incorporating PHB and PEG because it can prepare copolymers with good properties, such as toughness, strength, and so on. In this study, we adopted soil suspension system to estimate the biodegradability of a series of PHB/PEG multiblock copolymers with different compositions and block lengths. In the degradation process, the changes in weight loss, molecular weight, and tensile strength were periodically measured to determine the biodegradability, and the surface morphology was also observed by SEM. In contrast to pure PHB, the weight loss of the copolymer was relatively lower. On the other hand, the tensile strength and molecular weight experienced apparent decrease, and for BHG1000-3-1, they reached 46.7% and 77.7% of the initial value, respectively. SEM observation showed that the surface was covered with numerous erosion pits. All these indicate that the degradation indeed took place and long-chain molecules have been hydrolyzed into shorter ones. The crystallization behavior was also investigated by DSC and WAXD. The results showed that both the segments, PEG and PHB, can form crystalline phases at lower PHB contents ranging from 29% to 44%, and when PHB component was more than 60%, only PHB phase can crystallize.     

Probing the micellization of diblock and triblock copolymers of poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactide) and poly(ethylene glycol) in aqueous and NaCl salt solutions

The micelle formation of a series of amphiphilic block copolymers in aqueous and NaCl solutions was studied by a fluorescent probe technique using pyrene as a "model drug". These copolymers were synthesized from poly (ethylene glycol) (PEG) and l-lactide by a new calcium ammoniate catalyst. They had fixed PEG block lengths (44, 104 or 113 ethylene oxide units) and various poly(l-lactide) (PLLA) block lengths (15–280 lactide units). The critical micelle concentration (cmc) was found to decrease with increasing PLLA content. The distinct dissimilarity of the cmc values of diblock and triblock copolymers based on the same block length of PEG provided evidence for the different configurations of their micelles. It was also observed that the introduction of NaCl salt significantly contributed to a decrease in the cmcs of the copolymers with short PEG and PLLA blocks, while it had less influence on the cmcs of copolymers with long PEG or PLLA blocks. The dependence of partition coefficients ranging from 0.2×10⁵ to 1.9×10⁵ on the PLLA content in the copolymer and on the micelle configuration was also discussed. The contribution of NaCl salt to increasing the partition of pyrene into a micellar phase was observed.     

Synthesis and characterization of poly(L‐lactic acid)–poly(ε‐caprolactone) multiblock copolymers by melt polycondensation

An Erratum has been published for this article in J. Polym. Sci. Part A: Polym. Chem. (2004) 42(22) 5845 New multiblock copolymers derived from poly(L‐lactic acid) (PLLA) and poly(ε‐caprolactone) (PCL) were prepared with the coupling reaction between PLLA and PCL oligomers with ? NCO terminals. Fourier transform infrared (FTIR), ¹³C NMR, and differential scanning calorimetry (DSC) were used to characterize the copolymers and the results showed that PLLA and PCL were coupled by the reaction between ? NCO groups at the end of the PCL and ? OH (or ? COOH) groups at the end of the PLLA. DSC data indicated that the different compositions of PLLA and PCL had an influence on the thermal and crystallization properties including the glass‐transition temperature (T_g), melting temperature (T_M), crystallizing temperature (T_c), melting enthalpy (ΔH_m), crystallizing enthalpy (ΔH_c), and crystallinity. Gel permeation chromatography (GPC) was employed to study the effect of the composition of PLLA and PCL and reaction time on the molecular weight and the molecular weight distribution of the copolymers. The weight‐average molecular weight of PLLA–PCL multiblock copolymers was up to 180,000 at a composition of 60% PLLA and 40% PCL, whereas that of the homopolymer of PLLA was only 14,000. A polarized optical microscope was used to observe the crystalline morphology of copolymers; the results showed that all polymers exhibited a spherulitic morphology. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5045–5053, 2004     

Poly(epsilon-caprolactone)-poly(oxyethylene) multiblock copolymers bearing along the chain regularly spaced pendant amino groups

Poly(epsilon-caprolactone) (PCL) macromers (M(n) = 1.7-3.8 kDa) which contain one Z-protected -NH2 group per chain were synthesized by ring-opening polymerization of epsilon-caprolactone in the presence of Sn(oct)2 using as initiator a diamine prepared by condensation of N-Boc-1,6-hexanediamine and N(alpha)-Boc-N(epsilon)-Z-L-Lysine. The coupling of these macromers with -COCl end-capped poly(oxyethylene) (PEO), M(n) = 1.0 kDa, afforded amphiphilic multiblock poly(ether ester)s (PEEs) which have, along the chain, regularly spaced pendant protected amino groups. Deprotection, accomplished without chain degradation, yielded -NH2 groups available for further reactions. The molecular structure of macromers and PEEs was investigated by 1H NMR and SEC. DSC and WAXS analyses showed that macromers and copolymers were semicrystalline and their T(m) increased with increase in the molecular weight of PCL segments. The inherent viscosity values (0.25-0.30 dL x g(-1)), together with SEC analysis results, indicated moderate polymerization degrees.     

Synthesis of high‐molecular‐weight aliphatic–aromatic copolyesters from poly(ethylene‐co‐1,6‐hexene terephthalate) and poly(L‐lactic acid) by chain extension

A series of aliphatic–aromatic multiblock copolyesters consisting of poly(ethylene‐co‐1,6‐hexene terephthalate) (PEHT) and poly(L ‐lactic acid) (PLLA) were synthesized successfully by chain‐extension reaction of dihydroxyl terminated PEHT‐OH prepolymer and dihydroxyl terminated PLLA‐OH prepolymer using toluene‐2,4‐diisoyanate as a chain extender. PEHT‐OH prepolymers were prepared by two step reactions using dimethyl terephthalate, ethylene glycol, and 1,6‐hexanediol as raw materials. PLLA‐OH prepolymers were prepared by direct polycondensation of L ‐lactic acid in the presence of 1,4‐butanediol. The chemical structures, the molecular weights and the thermal properties of PEHT‐OH, PLLA‐OH prepolymers, and PEHT‐PLLA copolymers were characterized by FTIR, ¹H NMR, GPC, TG, and DSC. This synthetic method has been proved to be very efficient for the synthesis of high‐molecular‐weight copolyesters (say, higher than M_w = 3 × 10⁵ g/mol). Only one glass transition temperature was found in the DSC curves of PEHT‐PLLA copolymers, indicating that the PLLA and PEHT segments had good miscibility. TG curves showed that all the copolyesters had good thermal stabilities. The resulting novel aromatic–aliphatic copolyesters are expected to find a potential application in the area of biodegradable polymer materials. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5898–5907, 2009     

Photocurable biodegradable poly(ɛ-caprolactone)/poly(ethylene glycol) multiblock copolymers showing shape-memory properties

Biodegradable multiblock copolymers were synthesized by a polycondensation of poly(ɛ-caprolactone) (PCL) diols of molecular weight (MW)=3,000 and poly(ethylene glycol)s (PEG) of MW=3,000 with 4,4′-(adipoyldioxy)dicinnamic acid (CAC) dichloride as a chain extender in diphenyl ether at 180 °C for 2 h, and were characterized by GPC, ¹H-NMR, FTIR, UV, DSC, and WAXS. These photosensitive copolymers were irradiated by a 400-W high-pressure mercury lamp (λ>280 nm) from 5–60 min to form a network structure. The gel contents increased with irradiation time, and attained ca. 90% after 60 min for all copolymers. The degree of swelling in a distilled water at ambient temperature, and the rate of degradation in a phosphate buffer solution (pH 7.2) at 37 °C increased with increasing PEG components. The shape-memory tests were performed by a cyclic thermomechanical experiments for the photocured CAC/PCL/PEG (75/25) films. The film with a gel content of 57% showed the best shape-memory property with strain fixity rate of 100% and strain recovery rate of 88%.     

聚(L-乳酸)的成纤模压增强

用成纤模压法制备了弯曲强度和剪切强度分别为 2 50～ 2 80MPa和 1 70～ 1 85MPa的聚 (L 乳酸 )(PLLA)园棒 .由于PLLA对热的不稳定性 ,在模坯制备过程中 ,PLLA的分子量下降 65%～ 70 % ,但模压过程对分子量影响较小 .扫描电子显微镜 (SEM)显示PLLA模坯在模压过程中发生了取向形变并形成纤维结构 ,这是PLLA棒材的力学性能得以增强的主要原因 .差示扫描量热 (DSC)分析和X 射线衍射 (XRD)分析表明PLLA模压成棒后 ,PLLA的结晶熔点下降 ,微晶尺寸变小 ,而结晶度增大 .     

聚乙二醇-聚L-丙交酯嵌段共聚物结晶形貌研究

用偏光显微镜和原子力显微镜对比研究了PEG-PLLA嵌段共聚物在110℃或120℃等温结晶后的结晶形貌.发现在110℃时只有PEG5000-PLLA2300和PEG5000-PLLA6300在偏光显微镜下呈现环带球晶形貌,在原子力显微镜高度图中显示明显的环带,并具有交替凸凹起伏形貌.而PEG5000-PLLA12000球晶中没有出现环带形貌而是生成了规则的环线.在120℃时,PEG5000-PLLA12000的球晶中才生成了规则的环带图案,原子力显微镜也显示了其球晶具有明显的交替凸凹起伏形貌,说明过冷度直接影响环带球晶的生成.产生周期性凸凹起伏和明暗交替消光是由片晶沿着球晶的半径方向周期性扭转造成的,片晶在凸起部分是Edge-on取向,在凹下部分是Flat-on取向.