Enzymatic Synthesis and Characterization of Novel Polycarbonates Derived from 5-Allyloxy-1, 3-dioxan-2-one and 5, 5-Dimethyl-1, 3-dioxan-2-one

Aliphatic polycarbonates and their copolymers have been used in drug controlled release system and other biomedical applications due to their good biocompatibility, favorable mechanical properties and some elasticity1, such as poly(1, 3-dioxan-2-one)2 and…     

基于乳酸和β-丙氨酸的聚酯酰胺共聚物合成及降解

采用直接熔融共缩聚方法成功地制备了L-乳酸/β-丙氨酸共聚物, 用红外光谱、核磁共振、凝胶色谱和DSC等方法对共聚物结构进行了表征; 考察了催化剂用量、投料比、聚合反应时间和反应温度等聚合条件对产物分子量及其结晶性能的影响. 实验结果表明, 采用质量分数为1.5%的亚锡复合催化剂在180 ℃下真空反应15 h为最佳聚合条件, 所得到的产物具有相对最大的分子量; 随着β-丙氨酸投料比增加, 相应共聚物的分子量明显下降. 所得到的L-乳酸/β-丙氨酸共聚物具有良好的降解性能, 聚合时间和β-丙氨酸含量对材料的结晶性能和降解性能均有较大的影响.     

Enzymatic Synthesis and Characterization of Novel Amphiphilic Triblock Copolymer Poly（p-dioxanoneco-5-benzyloxytrimethylene carbonate）-block-poly（ethylene glycol）

In recent years, amphiphilic block copolymers consisting of hydrophilic and hydrophobic segments have attracted much attention, because of their unique phase behavior in aqueous media and potential applications as drug delivery systems1. Poly(ethylene gly…     

Synthesis and Characterization of Amphiphilic Block Copolymer Containing PVP and Poly(5-benzyloxytrimethylene carbonate)

Amphiphilic block copolymers have attracted great interest recently, especially for thebiomedical uses1, . The hydrophilic blocks improve the biocompatibility of copolymer, 2while the hydrophobic blocks enhance the mechanics of the material and providever…     

ε-己内酯与L-丙交酯共聚物的合成及其电纺丝加工初步研究

采用辛酸亚锡为催化剂,1,4-丁二醇为引发剂,制备了不同组成、不同分子量的ε-己内酯/L-丙交酯共聚物,并用GPC、FTIR、1H-NMR、DSC和XRD等分析方法表征了该共聚物的结构.结果表明通过改变初始投料中两单体的比例,可以调节共聚酯的分子结构;调节单体与引发剂的比例,可以调节共聚酯分子量,进而影响到其形态与性质.采用高分子量的共聚物进行电纺丝加工,得到了微米级超细纤维无纺布,由SEM可观察到纤维之间有不同程度的粘结.在孔隙率约为75%左右的情况下,该无纺布的抗拉强度可达6.1MPa,延伸率为500%.     

低分子量结晶性丙交酯/乙交酯与己内酯/乙交酯共聚物热转变温度的组成与分子量依赖性

以1,4-丁二醇为引发剂、辛酸亚锡为催化剂,通过L-丙交酯(LLA)、乙交酯(GA)、ε-己内酯(CL)的开环共聚,制得了低分子量的端羟基结晶性LLA/GA共聚物(PLLGA)和CL/GA共聚物(PCG),分别以FTIR1、H-NMR、GPC、DSC对其微结构和热转变温度进行了表征,重点考察了其热转变温度的组成、分子量依赖性.结果表明,利用辛酸亚锡/二元醇引发开环聚合,通过改变单体配比和单体/引发剂配比,可方便地调控共聚物的组成和分子量;通过改变共聚物的组成和分子量,可在较宽的范围内调节共聚物的热转变温度,并得到了玻璃化温度和熔点与组成、分子量之间定量的经验关系式.     

基于聚乙烯的无规和嵌段接枝共聚物的制备

采用乙烯配位聚合和巯基-烯点击化学相结合的方法制备了羟基封端的线性聚乙烯,末端羟基含量接近100%;利用酰氯与羟基的高效反应,将羟基封端的聚乙烯转化为降冰片烯封端的聚乙烯大单体(PE-NB).使用Grubbs II代催化剂,将大分子单体与降冰片烯(NB)单体进行开环易位共聚,通过调整单体的投料比和加料方式制备了分子量和组成可控的聚降冰片烯-g-聚乙烯(PNB-g-PE)接枝共聚物.其中,无规共聚时,大单体的转化率接近100%,所得无规接枝共聚物的重均分子量为1.79×10~4~3.14×10~4,分子量分布指数为2.09~2.60,聚乙烯链段的质量分数为4.6%~16.8%;而嵌段共聚时,由于空间位阻原因,大单体的转化率约为80%.热分析研究发现,由于空间位阻,接枝共聚物的结晶度较聚乙烯前驱体略有下降,且接枝度越大,结晶能力下降得越多.     

Metal-flee synthesis of amphiphilic functional polycarhonates

Amphiphilic block copolymers of poly（5-benzyloxy trimethylene carbonate） （PBTMC） and poly（ethylene glycol） （PEG） were synthesized through enzymatic polymerization using immobilized porcine pancreas lipase （IPPL）. The obtained copolymers with different compositions were characterized by GPC and IH NMR. The copolymer composition was in agreement with the feed ratio. The molecular weight of the copolymers showed an increasing trend with the decrease of PEG contents. MiceUes of the copolymers were formed by dialysis procedure, and characterized by transmission electron microscopy （TEM）.     

Metal-free synthesis of amphiphilic functional polycarbonates

Amphiphilic block copolymers of poly(5-benzyloxy trimethylene carbonate)(PBTMC) and poly(ethylene glycol)(PEG) were synthesized through enzymatic polymerization using immobilized porcine pancreas lipase(IPPL).The obtained copolymers with different compositions were characterized by GPC and ~1H NMR.The copolymer composition was in agreement with the feed ratio. The molecular weight of the copolymers showed an increasing trend with the decrease of PEG contents.Micelles of the copolymers were formed by dialysis procedure,and characterized by transmission electron microscopy (TEM).     

The influence of comonomer on ethylene/α-olefin copolymers prepared using [bis(N-(3-tert butylsalicylidene)anilinato)] titanium (IV) dichloride complex

We describe the synthesis of [bis(N-(3-tert-butylsalicylidene)anilinato)] titanium (IV) dichloride (Ti-FI complex) and examine the effects of comonomer (feed concentration and type) on its catalytic performance and properties of the resulting polymers. Ethylene/1-hexene and ethylene/1-octene copolymers were prepared through copolymerization using Ti-FI catalyst, activated by MAO cocatalyst at 323 K and 50 psi ethylene pressure at various initial comonomer concentrations. The obtained copolymers were characterized by DSC, GPC and 13C-NMR. The results indicate that Ti-FI complex performs as a high potential catalyst, as evidenced by high activity and high molecular weight and uniform molecular weight distribution of its products. Nevertheless, the bulky structure of FI catalyst seems to hinder the insertion of α-olefin comonomer, contributing to the pretty low comonomer incorporation into the polymer chain. The catalytic activity was enhanced with the comonomer feed concentration, but the molecular weight and melting temperature decreased. By comparison both sets of catalytic systems, namely ethylene/1-hexene and ethylene/1-octene copolymerization, the first one afforded better activity by reason of easier insertion of short chain comonomer. Although 1-hexene copolymers also exhibited higher molecular weight than 1-octene, no significant difference in both melting temperature and crystallinity can be noticed between these comonomers.     

“Living”/controlled radical copolymerization of N-phenylmaleimide and styrene using Fréchet-type dendritic initiators

Polyarylether dendrons as macroinitiators for the "living"/controlled free radical copoly-merization of N-phenylmaleimide (PhMI) and styrene (St) have been demonstrated. The copoly-merization was carried out in bulk or anisole with CuBr/bipy catalyst at 100-130℃. It is found that the resulting copolymers possess predetermined molecular weights and narrower polydispersities (1.18 < Mw/Mn<1.32). The effects of reaction temperature and monomer feed on the copolymeri-zation kinetics were investigated in detail. By using the Fineman-Ross method, the apparent monomer reactivity ratios for the atom transfer radical copolymerization of PhMI and St were determined to be rphM1 = 0.0207, and rst = 0.0484, respectively.     

RANDOM COPOLYMER OF PROPYLENE OXIDE AND ETHYLENE OXIDE PREPARED BY DOUBLE METAL CYANIDE COMPLEX CATALYST

Copolymerization of propylene oxide (PO) and ethylene oxide (EO) using double metal cyanide (DMC) complexas the catalyst was carried out. The structure of random copolymers was confirmed by ~(13)C-NMR and IR spectra. ~1H-NMRanalysis shows that the EO content in the copolymer is the same as that in the initial monomer feed. Moderate molecularweight copolymers with various EO content were obtained and their values of molecular weigh distribution (MWD) fell inthe range of 1.21-1.55. It was found that the molecular weight of copolymers is controlled by the mass ratio of EO + PO toinitiator moles used. The reaction rate as well as polymer yield decrease with increasing EO content in the feed composition.     

本体共聚合制备丙烯/1-丁烯合金及表征

以球形高效负载的TiCl₄/MgCl₂/邻苯二甲酸二异丁酯(DIBP)为催化剂, 采用本体聚合方法进行丙烯与1-丁烯共聚合研究. 考察了共单体效应对共聚活性及聚合物立构规整性的影响; 表征了共聚物的结构. 结果表明, 随着1-丁烯/丙烯投料比的增加, 聚合活性呈先升高后降低的趋势, 在1-丁烯/丙烯摩尔投料比为0.26条件下聚合活性达到最高, 并随着共聚物中1-丁烯含量的增加, 共聚物的熔点明显下降, 分子量降低, 分子量分布变窄, 同时共聚物力学性能有明显提高, 透明度逐渐增加.     

Olefin copolymerization with metallocene catalysts. I. Comparison of catalysts

A number of metallocene/methylaluminoxane (MAO) catalysts have been compared for ethylene/propylene copolymerizations to find relationship between the polymerization activities, copolymer structures, and copolymerization reactivity ratio with the catalyst structures. Stereorigid racemic ethylene bis (indenyl) zirconium dichloride and the tetrahydro derivative exhibit very high activity of 10 ⁷ g (mol Zr h bar)^?1, giving copolymers having comonomer compositions about the same as the feed compositions, molecular weights increasing with the increase of ethylene in the feed, random incorporation of comonomers, and narrow molecular weight distribution indicative of a single catalytic species. Nonbridged bis (indenyl) zirconium behaved differently, favoring the incorporation of ethylene over propylene, producing copolymers whose molecular weight decreases with the increase of ethylene in the feed, broad molecular weight distribution, and a methanol soluble fraction. This catalyst system contains two or more active species. Simple methallocene catalysts have much lower polymerization activities. C_pTiCl₂/MAO produced copolymers with tendency toward alternation, whereas Cp₂HfCl₂/MAO gave copolymer containing short blocks of monomers.     

Synthesis and Characterization of Hybrid Biopolymers of L-lactic Acid and 2-Pyrone-4,6-dicarboxylic Acid

Copolymers of L-lactic acid (LA) and 2-pyrone-4,6-dicarboxylic acid (PDC), a chemically stable metabolic intermediate of lignin, were prepared by dehydrated polycondensation based on stepwise oligomerization followed by post-polymerization in vacuo. When the polymerization was performed in the presence of methanesulfonic acid as a catalyst, the molecular weights of the resulting copolymers were sufficiently high. Furthermore, expansion of the polymeric surface area was found to be an important factor in facilitating dehydration and thereby producing high molecular weight polymers. PDC feed ratio significantly affected the molecular weight because of the different polymerization capability from LA. Relationship between the PDC feed ratio and the molecular weight of the resulting polyesters was for the first time demonstrated quantitatively. The obtained copolymers were characterized by ¹H- and ¹³C-NMR, IR, and thermal analysis. The high molecular weight copolymers possessed the higher decomposition temperatures than PLLA and their fusible temperature ranges were reasonably expanded.     

含苯并咪唑酮结构双酚A型聚芳醚酮共聚物的制备和表征

通过双酚A-4, 4'-二氟二苯甲酮-苯并咪唑酮(BPA-DFK-HBI)无规共聚得到一系列聚芳醚酮共聚物。 采用亲核缩聚和C-N偶联缩聚的方法, 获得了高相对分子质量聚合物。 通过红外、核磁等技术手段表征了聚合物的结构, DSC、TGA分析了聚合物的热性能。 结果表明, 随着苯并咪唑酮加入量的增大, 共聚物对DMF、NMP等极性溶剂的耐溶剂性能得到提升, 热稳定性增强, 玻璃化转变温度(T_g)也明显提高, T_g最高可达236 ℃。 当苯并咪唑酮与双酚A的摩尔比大于7:3时, 溶解性降低, 反应出现前期沉淀, 难以得到高相对分子质量的聚合物。     

聚苯乙烯-b-聚硅氧烷-b-聚苯乙烯三嵌段共聚物的合成及表征

采用乙烯基封端的聚 (二甲基硅氧烷 )与溴化氢反应制得末端含有C Br的双官能聚 (二甲基硅氧烷 ) ,以此聚 (二甲基硅氧烷 )大分子为引发剂 ,CuCl为催化剂 ,4 ,4′ 二 (5 壬基 ) 2 ,2′ 联吡啶为配体 ,通过原子转移自由基聚合法 ,制得分子量和结构可控的聚苯乙烯 b 聚硅氧烷 b 聚苯乙烯 (PSt b PDMS b PSt)共聚物 .     

聚芳醚腈-聚硅氧烷嵌段共聚物的合成

采用4-烯丙基-2-甲氧基苯酚(Eugenol)为端基的聚二甲基硅氧烷与氟代苯端基含杂萘联苯结构聚芳醚腈,以碳酸钾为催化剂,二甲基亚砜与邻二氯苯为溶剂的条件下进行芳香亲核取代反应(SNAr),合成了一种高分子量的聚芳醚腈-聚硅氧烷嵌段共聚物,并采用FTIR和1H-NMR对该产物的结构进行了表征.DSC测试结果表明该类嵌段共聚物具有两个玻璃化转变温度(Tg),分别为-98～-90℃和255～287℃,而且共聚物具有优良的耐热性,10%的热失重温度(Td)在450℃以上.采用原子力显微镜和透射电镜观测发现该共聚物存在明显的相分离特征.     

Lipase-catalysed degradation of copolymers prepared from ?-caprolactone and dl-lactide

A series of copolymers were prepared by ring-opening polymerization of ?-caprolactone and dl-lactide, using zinc lactate as catalyst. The resulting PCL/PLA copolymers were characterized by various analytical techniques such as NMR, SEC, DSC and X-ray diffraction. The [CL]/[LA] ratios of the copolymers are very close to those in the feed, indicating a good conversion of monomers. The copolymers with CL contents higher than 50% appear semi-crystalline, the crystalline structure being of the PCL-type. Compression moulded polymer films were allowed to degrade in a pH = 7.6 phosphate buffer containing Pseudomonas lipase. Data show that copolymers with CL contents lower than 25% are not degradable and the degradation rate increases with CL content for CL-rich copolymers. Various soluble degradation products are detected in the degradation medium, including CL₁ to CL₃ and LA₁ to LA₄ homo-oligomers, and CL₂LA₁ co-oligomer. The presence of LA homo-oligomers and CL₂LA₁ co-oligomer suggests that Pseudomonas lipase can not only degrade PCL but also LA short blocks along PCL/PLA copolymer chains. On the other hand, little changes of composition are detected during degradation, in agreement with a surface erosion mechanism as shown by ESEM.     

带双键侧链的二氧化碳三元共聚物的合成及性能研究

二氧化碳和环氧丙烷共聚物的玻璃化温度处于35～40℃,在低于20℃的环境下脆性很大.在稀土三元催化剂Y(CCl3COO)3ZnEt2甘油(glycerine)下实现了CO2、环氧丙烷(PO)和烯丙基缩水甘油醚(AGE)的三元共聚,合成了侧链带双键的二氧化碳共聚物,其玻璃化温度(Tg)为-15.4～36.1℃,大幅度拓展了二氧化碳共聚物的低温区使用范围.