过氧化物引发交联聚ε-己内酯的研究

以过氧化苯甲酰(BPO)为引发剂,对聚ε-己内酯(PCL)进行交联,研究了过氧化物含量,交联温度和交联时间对交联反应的影响,较高的交联温度可以提高BPO引发交联反应的速率.采用DSC、WAXD和DMA等方法对交联后聚ε-己内酯的结晶行为、玻璃化转变、力学性能及其生物降解特性进行了研究.结果表明,交联PCL的结晶度下降,熔点降低,玻璃化转变温度降低,但结晶温度有所提高.交联PCL的断裂伸长率和杨氏模量均下降.但是仍具有完全的生物降解能力.     

ε-己内酯开环聚合金属配合物催化剂研究进展

聚己内酯(PCL)具有良好的环境相容性和生物医学领域中潜在应用价值,成为近年来研究的热点课题.聚己内酯(PCL)制备方式就是催化ε-己内酯(ε-caprolactone)开环聚合,其所用催化剂对控制聚合过程和调控所得聚己内酯结构起着关键作用,并影响所得聚合物的性能和应用前景.一个重要的环节就是筛选出高活性和能够良好调控...     

原位生成三苄氧基钇催化ε-己内酯可控开环聚合

以烷基钇[Y( CH2 SiMe3),(THF)2]与苯甲醇原位反应生成的三苄氧基钇为引发剂,研究ε-己内酯(CL)可控开环聚合反应(ROP).结果表明,随着聚合体系中单体/引发剂摩尔比的增大,产物聚己内酯(PCL)的数均分子量(1H NMR计算和GPC测定)均随之线性增加,且分子量分布(Mw/Mn=1.4～1.1)逐...     

酶促开环聚合与自缩合乙烯基共聚合相结合制取超支化聚合物

在Novozyme 435脂肪酶催化下, 甲基丙烯酸羟乙酯(HEMA)引发己内酯(ε-CL)开环聚合反应, 得到一端为双键, 另一端为羟基的直链聚己内酯(PCL)产物; 将其端羟基官能化得到大分子AB*型单体, 与苯乙烯以原子转移自由基聚合(ATRP)反应形式进行自缩合乙烯基共聚合, 得到超支化结构聚苯乙烯-b-聚己内酯产物.     

磁性PCL-PEG-PCL微球的制备及释药性研究

以聚乙二醇引发ε-己内酯开环聚合得到聚己内酯-聚乙二醇-聚己内酯(PCL-PEG-PCL)共聚物,双乳化-有机溶剂挥发法制得载药磁性PCL-PEG-PCL微球,并对微球进行一系列表征及研究其磁响应释药行为.FT-IR结果表明PEG接枝上PCL;GPC结果表明共聚物分子量分布均匀;SEM结果表明微球呈球性良好;XRD结果...     

电子束辐照法制备交联共混物聚(ε-己内酯)/苯乙烯-丙烯腈共聚物的结晶动力学研究

将线形聚(ε-己内酯)(PCL)、苯乙烯-丙烯腈共聚物(SAN)和三烯丙基异三聚氰酸酯(TAIC)熔融共混,通过电子束辐照法制备了3组凝胶含量不同的交联PCL和PCL/SAN共混物样品.采用相差显微镜(PCOM)观察发现PCL与SAN具有良好的相容性.利用示差扫描量热法(DSC)和偏光显微镜(POM)研究了交联PCL和PCL/SAN共混物的等温结晶动力学和非等温结晶行为.结果表明,当体系交联程度相近时,交联聚己内酯的结晶动力学随SAN含量的增加而明显减慢.在SAN含量相同时,交联聚己内酯的结晶速率随交联程度增大而减小.对分离提取的线形和交联组分进行结晶动力学的研究则表明SAN引入对PCL的结晶速率起到了关键性的抑制作用.     

由活性大分子环状前体合成环状聚ε-己内酯接枝聚L-乳酸

由2,2-二丁基-2-锡-1,3-二氧环庚烷引发ε-己内酯开环聚合制得环状聚ε-己内酯(3);3与活性单体α-(1-丙烯酰氧乙基)-ε己内酯反应,合成了活性环状聚ε-己内酯(5);5在UV辐照下发生分子内交联反应制得活性大分子引发剂6;6引发L-丙交酯接枝共聚合制得环状聚ε-己内酯接枝聚L-乳酸,其结构经NMR,SEC和DSC表征。     

聚乳酸/聚己内酯/聚(ε-己内酯-L-丙交酯)共聚物三元共混体系的结构与性能

通过开环共聚合,合成了3种不同单元比例的ε-己内酯(ε-CL)与L-丙交酯(L-LA)的共聚物P(CLco-LA)。通过熔融共混制备了聚乳酸(PLA)/聚己内酯(PCL)/P(CL-co-LA)三元共混材料,研究了P(CL-coLA)对共混材料微观形貌、热性能以及力学性能的影响。结果表明,共聚物P(CL-co-LA)作为PLA/PCL不相容体系的界面增容剂,减小了PCL分散相的尺寸,改善了PLA/PCL共混体系的相容性,提高了共混材料的韧性。固定m(PLA)∶m(PCL)∶m(P(CL-co-LA))=80∶20∶10时,以P(CL49/LA51)(其中数字代表摩尔分数(%))作为界面增容剂效果最佳,共混材料的断裂伸长率可达到(210±30)%。     

1,6-己二醇选择氧化内酯化制备ε-己内酯

ε-己内酯是合成聚己内酯(PCL)等聚合物的关键单体,相关高分子材料具有良好的生物降解性和兼容性,在生物医药、环保材料等领域具有重要应用。ε-己内酯的绿色廉价制备是制约这类材料广泛使用的重要因素,其中1,6-己二醇选择氧化内酯化制备ε-己内酯有待进一步发展。本文分析对比了环己酮Baeyer-Villiger氧化法和1,6-己二醇氧化内酯化法制备ε-己内酯的优缺点,按照反应体系中是否加入电子受体(氧化剂)分类介绍了国内外1,6-己二醇选择氧化内酯化制备ε-己内酯相关的研究进展,并对相应反应体系、所用催化剂的优缺点进行了评述,最后对该转化过程的发展趋势进行了展望。     

原位生成三苄氧基钇催化ε-己内酯可控开环聚合

本文研究了以烷基钇[Y(CH2SiMe3)3(THF)2]与苯甲醇原位反应生成的三苄氧基钇为引发剂的ε-己内酯(CL)可控开环聚合。研究结果表明,随着聚合体系中单体/引发剂摩尔比的增大,由1H-NMR计算和GPC测定得到的产物聚己内酯(PCL)的数均分子量均随之线性增加,且分子量分布(Mw/Mn =1.4～1.1)逐渐变窄;1H-NMR计算所得PCL的数均分子量与由单体/引发剂投料比计算得到的理论值一致,表明该体系催化的CL开环聚合具有很好的可控性。1H-NMR分析显示产物PCL的端基分别为苯甲醇酯和醇羟基,由此提出了可能的开环聚合机理。     

聚苯乙烯-聚4-乙烯吡啶两亲性嵌段共聚物与新型荧光分子的自组装

合成了新型温敏荧光小分子,并利用活性/可控自由基聚合中的可逆加成-断裂链转移聚合反应(RAFT)合成了聚苯乙烯-聚4-乙烯吡啶两亲性嵌段共聚物(PS-b-P4VP);采用傅立叶变换红外光谱仪和凝胶渗透色谱仪分别测定了其结构和相对分子质量.将荧光小分子和PS-b-P4VP一同在甲苯或CO2气体膨胀甲苯环境中进行自组装,采用透射电子显微镜观察了其胶束形态.结果表明,CO2气体膨胀甲苯的引入对胶束的形态无明显影响.     

Synthesis of four‐armed poly(ε‐caprolactone)‐block‐poly(ethylene oxide) by diethylzinc catalyst

Biodegradable, amphiphilic, four‐armed poly(?‐caprolactone)‐block‐poly(ethylene oxide) (PCL‐b‐PEO) copolymers were synthesized by ring‐opening polymerization of ethylene oxide in the presence of four‐armed poly(?‐caprolactone) (PCL) with terminal OH groups with diethylzinc (ZnEt₂) as a catalyst. The chemical structure of PCL‐b‐PEO copolymer was confirmed by ¹H NMR and ¹³C NMR. The hydroxyl end groups of the four‐armed PCL were successfully substituted by PEO blocks in the copolymer. The monomodal profile of molecular weight distribution by gel permeation chromatography provided further evidence for the four‐armed architecture of the copolymer. Physicochemical properties of the four‐armed block copolymers differed from their starting four‐armed PCL precursor. The melting points were between those of PCL precursor and linear poly(ethylene glycol). The length of the outer PEO blocks exhibited an obvious effect on the crystallizability of the block copolymer. The degree of swelling of the four‐armed block copolymer increased with PEO length and PEO content. The micelle formation of the four‐armed block copolymer was examined by a fluorescent probe technique, and the existence of the critical micelle concentration (cmc) confirmed the amphiphilic nature of the resulting copolymer. The cmc value increased with increasing PEO length. The absolute cmc values were higher than those for linear amphiphilic block copolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 950–959, 2004     

Preparation of electrospun luminescent polyimide/europium nanofibers by simultaneous in situ sol-gel and imidization processes

Comicellization of a star block copolymer poly(ε-caprolactone)-block-poly(diethylamino)ethyl methacrylate (S(PCL-b-PDEAEMA)) and a linear block copolymer methoxy poly(ethylene glycol)-block-poly(ε-caprolactone) (mPEG-b-PCL) was developed to enhance the stability and lower the cytotoxicity of the micelles. The two copolymers self-assembled into the mixed micelles with a common PCL core surrounded by a mixed PDEAEMA/mPEG shell in aqueous solution. This core-shell structure was transformed to the core-shell-corona structure at high pH due to the collapse of the PDEAEMA segment. The properties of the polymeric micelles were greatly dependent on the weight ratio of the two copolymers and the external pH. As increasing the mPEG-b-PCL content, the size and the zeta potential of the mixed micelles were lowered while the pH-dependent stability and the biocompatibility were improved. Moreover, an increase in pH accelerated the release of indomethacin (IND) from the mixed micelles in vitro. These results augured that the mixed micelles could be applied as a stable pH-sensitive release system.     

Synthesis,characterization, and solution behavior of well-defined double hydrophilic linear amphiphilic poly (N-isopropylacrylamide)-b-poly (ε-caprolactone)-b-poly (N-isopropylacrylamide) triblock copolymers

Well-defined linear dihydrophilic amphiphilic ABA-type triblock copolymers of ε-caprolactone (CL) and N-isopropylacrylamide (NIPAAm) have successfully been synthesized with a high yield by combining the ring opening polymerization (ROP) and xanthate-mediated reversible addition-fragmentation chain transfer (RAFT) polymerization methods. The resulted block copolymer shows the formation of micelles in water as supported by light scattering. The critical micelle concentration (cmc) value of the micelle increases with the increase in the chain length of the poly (N-isopropylacrylamide) (PNIPAAm) block. Cloud point of the block copolymers decreases with the decrease in the PNIPAAm chain length. The TGA analysis shows a one-step degradation and a lower thermal stability of the triblock copolymer than the PNIPAAm. The DSC analysis of the triblock copolymer shows the lowering of glass transition temperature (T _g), and melting temperature (T _m) peaks possibly due to the partial miscibility of the poly (ε-caprolactone) (PCL) block with the amorphous PNIPAAm block through the interaction of ester groups of PCL with the amide groups of PNIPAAm. The XRD pattern of the triblock copolymer shows a broad peak due to the suppression of the crystallization of PCL block owing to the mixing of PNIPAAm block with the PCL block.     

AN APPROACH TO SYNTHESIZE POLY(ETHYLENE GLYCOL)-b-POLY(ε-CAPROLACTONE) WITH TERMINAL AMINO GROUP via SCHIFF'S BASE AS AN INITIATOR

A new method to synthesize a degradable terminal amino group-containing copolymer, poly(ethylene glycol)-b-poly(ε-caprolactone) (MPEG-PCL-NH2), was developed in the following three steps: (1) the ring-opening polymerization (ROP) of ε-caprolactone from the Schiff base prepared from benzaldehyde and ethanolamine (Ph-CH=NCH2CH2OH) used as an initiator to obtain heterobifunctional poly(ε-caprolactone) with one terminal Schiff base group and one hydroxyl group (HO-PCL-CH2CH2N = CH-Ph); (2) the coupling reaction of two reactive precursors, a hydroxy-terminated HO-PCL-CH2CH2N=CH-Ph and α-monocarboxy-ωmonomethoxy poly(ethylene glycol) (CMPEG) to synthesize MPEG-PCL-CH2CH2N=CH-Ph; (3) the conversion of the -N=CH-Ph end-group into NH2 end-group by acidification of acetic acid to obtain MPEG-PCL-NH2. The structures from the precursors to the terminal amino group-containing copolymer were confirmed by 1H-NMR and their molecular weights were measured by gel permeation chromatography. The amphiphilic terminal amino group-containing copolymer could self-assemble into micelles in an aqueous system with PCL block as the core and PEG block as the shell. The micelle formation of the terminal amino group-containing block copolymer was studied by fluorescent probe technique and the existence of critical micellar concentration (cmc) confirmed the amphiphilic nature of the resulting copolymer. ESEM and DLS analysis of the micelles revealed a homogeneous spherical morphology and a unimodal size distribution.     

以PEO-b-PAN嵌段共聚物胶束作模板合成SiO_2-C纳米复合材料

通过阴离子聚合和活性自由基聚合相结合的方法,合成了聚环氧乙烷-聚丙烯腈两亲性嵌段共聚物(PEO-b-PAN).PEO-b-PAN嵌段共聚物在水溶液中自组装形成胶束正硅酸乙酯以胶束作模板进行溶胶-凝胶过程,形成SiO2/PEO-b-PAN复合材料.随后经300℃预氧化,1000℃高温炭化,得到SiO2-C纳米复合材料.用1HNMR、IR、GPC、TGA、TEM、SEM等技术对嵌段共聚物及SiO2-C纳米复合材料进行了表征,结果表明SiO2-C复合材料的结构为SiO2为壳C为核的纳米粒子,粒子的直径为(55±5)nm.     

树枝状聚(醚-酰胺)基胶束的制备及其形貌研究

采用ε-己内酯(CL)开环聚合的方法首先合成树枝状聚(醚-酰胺)基(DPEA)星形聚合物star-PCL,再与异氰酸基封端的PEG(PEG-NCO)偶合制备了两亲性树枝状聚(醚-酰胺)基星形嵌段聚合物star-PCL-b-PEG.利用FT-IR、1H-NMR和GPC分析测试手段对star-PCL-b-PEG的结构进行了表征.通过滴加选择性溶剂的方法,制备了star-PCL-b-PEG以水为介质的类似"平头"聚集体胶束溶液.采用荧光光谱法测得star-PCL-b-PEG水溶液的临界胶束浓度(CMC)为1.623mg/L;采用激光光散射仪测得其在浓度0.15mg/mL和0.5mg/mL的流体力学半径分别为86.2nm和224.6nm,其多分散指数分别为0.115和0.197.透射电镜(TEM)观察发现胶束的形貌受共溶剂的特性,初始聚合物浓度,水含量等因素的影响.     

Association behavior of fluorine-containing and non-fluorine-containing methacrylate-based amphiphilic diblock copolymer in aqueous media

Fluorine-containing amphiphilic block copolymers, poly(sodium methacrylate)-block-poly(nonafluorohexyl methacrylate) (NaMAm-b-NFHMAn) (m:n = 61:12, 72:33, 64:57), and the corresponding non-fluorine-containing amphiphilic block copolymer, poly(sodium methacrylate)-block-poly(hexyl methacrylate) (NaMAm-b-HMAn) (m:n = 64:10, 69:37, 67:50), were synthesized. Both polyNaMA-b-polyNFHMA and polyNaMA-b-polyHMA formed micelles above critical micelle concentrations, (cmc's), around 3 x 10(-5) to 1 x 10(-4) mol/L, while neither polymer decreased surface tension of aqueous solutions. The size and shape of the micelles were examined by dynamic light scattering, small-angle neutron scattering, and small-angle X-ray scattering. PolyNaMA-b-polyHMA appeared to form only spherical micelles, while polyNaMA-b-polyNFHMA with a long NFHMA segment formed both spherical and rodlike micelles. The micelles of fluorine-containing block copolymers were obviously larger than those of non-fluorine-containing block copolymers with the same chain length and the same hydrophilic/hydrophobic chain ratio. The fluorine-containing block copolymer selectively solubilized fluorinated dye into the water phase when a mixture of decafluorobiphenyl and 2,6-dimethylnaphthalene was added to the micelle solution.     

Conventional synthesis of amphiphilic block copolymer utilized for polymeric micelle by mechanochemical solid-state polymerization

The first example is presented here of an amiphiphilic block copolymer synthesized by mechanochemical solid-state polymerization and used to form polymeric micelles. A model amphiphilic block copolymer was synthesized first, possessing galactose as a hydrophilic side chain and theophylline as a hydrophobic side chain, by mechanochemical solid-state polymerization. The resulting copolymer had a narrow molecular weight distribution. Polymeric micelle formation was subsequently carried out with the copolymer by a dialysis method. To gain insight into the physicochemical properties of the polymeric micelle, dynamic light scattering (DLS) measurements were performed. A narrow distribution of diameters was observed in the polymeric micelle solution, and these micelles were disrupted by the addition of sodium dodecyl sulfate (SDS). It was also confirmed by DLS measurements that the polymeric micelles were spherical. These results suggested that the block copolymer synthesized by mechanochemical solid-state polymerization was as suitable for the preparation of polymeric micelles as materials obtained by living polymerization.     

Micellization phenomena of biodegradable amphiphilic triblock copolymers consisting of poly(beta-hydroxyalkanoic acid) and poly(ethylene oxide)

This paper reports the studies on micelle formation of new biodegradable amphiphilic poly(ethylene oxide)-poly[(R)-3-hydroxybutyrate]-poly(ethylene oxide) (PEO-PHB-PEO) triblock copolymer with various PHB and PEO block lengths in aqueous solution. Transmission electron microscopy showed that the micelles took an approximately spherical shape with the surrounding diffuse outer shell formed by hydrophilic PEO blocks. The size distribution of the micelles formed by one triblock copolymer was demonstrated by dynamic light scattering technique. The critical micellization phenomena of the copolymers were extensively studied using the pyrene fluorescence dye absorption technique, and the (0,0) band changes of pyrene excitation spectra were used as a probe for the studies. For the copolymers studied in this report, the critical micelle concentrations ranged from 1.3 x 10(-5) to 1.1 x 10(-3) g/mL. For the same PEO block length of 5000, the critical micelle concentrations decreased with an increase in PHB block length, and the change was more significant in the short PHB range. It was found that the micelle formation of the biodegradable amphiphilic triblock copolymers consisting of poly(beta-hydroxyalkanoic acid) and PEO was relatively temperature-insensitive, which is quite different from their counterparts consisting of poly(alpha-hydroxyalkanoic acid) and PEO.