New approaches to hyperbranched poly(4‐chloromethylstyrene) and introduction of various functional end groups by polymer‐analogous reactions

A facile way for the synthesis of hyperbranched poly(4‐chloromethylstyrene) [P(4‐CMS)] with adjustable molar mass by classic atom transfer radical polymerization (ATRP) and mechanistically similar procedures is presented. Subsequently, the chlorine functional groups have been modified to obtain polymers with different polarities. On the one hand, the polymer was end‐capped with unpolar groups (e.g., methyl, phenol ether) to obtain chemically inert substances. On the other hand, more complex functional groups have been introduced through azide groups by 1,3‐dipolar cycloaddition reaction (“click chemistry”). Furthermore, a method for the introduction of ester groups under mild conditions using cesium carboxylates is presented, which also allowed the preparation of so‐called hyperstars by attaching COOH functionalized polystyrene chains onto the P(4‐CMS) as core molecule. All these reactions were carried out in high or very high yields. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2224–2235, 2010     

支化PEG-b-PCL嵌段共聚合物的合成

以聚乙二醇甲基丙烯酸酯(PEGMA)为大分子引发剂进行ε-己内酯的酶催化开环聚合, 合成出嵌段共聚物, 然后将其转化成大分子引发剂型单体(Macroinimer), 最后通过原子转移自由基聚合(ATRP)制备出一种新型结构的嵌段型支化聚合物.     

A new method for synthesizing hyperbranched polymers with reductive groups using redox/RAFT/SCVP

The novel hyperbranced polymers containing reductive groups were successfully prepared and characterized using redox/reversible addition fragmentation chain transfer(RAFT)/self-condensing vinyl polymerization(SCVP) method. Several redox initiating chemicals such as Cu(III)/―CONH2, Ce(IV)/―CONH2 and Ce(IV)/―OH were chosen to increase the free radical generating rate, and the chain transfer agent(CTA) was used to reduce the molecular chain propagating rate, in order to obtain polymers with high degree of branching. Detailed analyses based on the molecular weight, ? value and the degree of branching of polymers(DB) obtained from 1H-NMR spectra and multi detector size exclusion chromatography(MDSEC) suggested the acquiring of hyperbranced polyacrylamides with Cu(III)/―CONH2 and Ce(IV)/―CONH2 as initiator in the presence of the CTA. Meanwhile, the as-prepared poly(N-hydroxymethyl acrylamide)(PNHAM) with higher DB value(0.48) proved that using Ce(IV)/―OH as the initiator could increase the free radical generating rate and diminish the gap between the propagating rate and the initiation rate during the reaction procedure. In addition, the effect of oxidant concentration on the Mark-Houwink index(?) value and the DB was also studied.     

多重响应性超支化星形聚合物的合成与组装以及控制释放研究

含二硫键的自引发单体与2-(2-甲氧基乙氧基)乙基甲基丙烯酸酯(MEO₂MA)进行自缩合乙烯基共聚合得到超支化PMEO₂MA(H-PMEO₂MA). 以它作大分子引发剂, 引发二甲氨基乙基甲基丙烯酸酯(DMAEMA)进行原子转移自由基聚合, 合成了具有温度、pH以及氧化还原多重响应性的超支化星形聚合物H-PMEO₂MA-star-PDMAEMA. 证明了H-PMEO₂MA有低临界溶液温度(LCST); 研究了PDMAEMA 链段的长度和溶液的pH值对超支化星形聚合物的LCST的影响. 当H-PMEO₂MA-star-PDMAEMA水溶液温度从2 ℃升高至室温, H-PMEO₂MA变成疏水性而发生聚集, 形成以H-PMEO₂MA为核, PDMAEMA为壳的胶束. 在胶束形成过程中, 将尼罗红装载到这种聚合物胶束中, 形成释药系统, 研究了pH、氧化还原响应性释药性能.     

Halloysite nanotubes grafted hyperbranched (co)polymers via surface-initiated self-condensing vinyl (co)polymerization

Halloysite nanotubes (HNTs) grafted hyperbranched polymers were prepared by the self-condensing vinyl polymerization (SCVP) of 2-((bromoacetyl)oxy)ethyl acrylate (BAEA) and the self-condensing vinyl copolymerization of n-butyl acrylate (BA) and BAEA with BAEA as inimer (AB*) respectively, from the surfaces of the 2-bromoisobutyric acid modified halloysite nanotubes (HNTs-Br) via atom transfer radical polymerization (ATRP) technique. The halloysite nanotubes grafted hyperbranched polymer (HNTs-HP) and the halloysite nanotubes grafted hyperbranched copolymer (HNTs-HCP) were characterized by elemental analysis (EA), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and transmission electron microscope (TEM). The grafted hyperbranched polymers were characterized with Nuclear magnetic resonance (NMR) and the molecular ratio between the inimer AB* and BA in the grafted hyperbranched copolymers was found to be 3:2, calculated from the TGA and EA results.     

非等速率自缩合乙烯基聚合反应产物的支化度

分析了一般的非等速率自缩合乙烯基聚合反应(SCVP)所生成的超支化聚合物体系的结构单元和支化度. 详细计算了支化度随反应进程(A基团转化率x)、活性的A*和B*基团反应速率比(r)和活化剂/单体物质的量比(α)的变化关系. 对任何指定的r和α组合, 随x的增加而单调增加, 对确定的x, 当α＜x/(1＋ )时, 随r的增加而单调减少, 当 α＞x/(1＋ )时, 随r的变化不再是单调的, 有极大值, 但无论怎样的r和α组合, 最大的支化度都只有0.5. 要想进一步提高产物的支化度, 可以在反应终了时, 在体系中再加入适当的其它单体, 使活化基团全部反应掉, 从而可使支化度达到2α/(1＋α).     

Synthesis and characterization of two classes of hyperstar polymers bearing hyperbranched cores grafted with linear arms

New hyperstar polymers (HSP) consisting of two different hyperbranched (hb) aromatic/aliphatic cores grafted with linear polymer arms were successfully synthesized. The hb cores were based on either hb poly(vinylbenzylchloride) synthesized by SCVP‐ATRP or hb polyester from a polycondensation reaction. For the core‐first approach, the hb cores have been modified to hb macroinitiators initiating either the cationic ring‐opening polymerization of oxazolines (Oxa) or the atom transfer radical polymerization of alkylmethacrylates. For potential use as reactive binders in epoxy coatings the HSPs were equipped with a defined amount of OH‐groups during arm growth via controlled block‐copolymerization with nonfunctionalized and OH‐functionalized monomers, either an oxazoline (OH)Oxa (2‐[1‐(hydroxymethyl)ethyl]‐oxazoline) or a methacrylate HEMA (2‐hydroxyethyl methacrylate). The amount of OH‐groups could be well adjusted in this way. The hyperstars were comprehensively characterized with respect to chemical structure and molecule dimension. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 000: 000–000, 2012     

含香豆素基团超支化星形聚合物的合成与表征

设计并合成了含有香豆素基团的自引发单体, 与2-(2-甲氧基乙氧基)乙基甲基丙烯酸酯(MEO₂MA)进行自缩合乙烯基共聚合后得到超支化聚合物H-PMEO₂MA. 以其作为大分子引发剂, 进行二甲氨基乙基甲基丙烯酸酯(DMAEMA)的原子转移自由基聚合, 合成了具有温度响应性的超支化星形聚合物H-PMEO₂MA-star-PDMAEMA. 将此超支化星形聚合物在水中自组装成胶束后, 利用支化点处香豆素基团的光二聚性能, 在λ=320 nm的紫外光照射下进行香豆素间的光交联反应, 形成核交联胶束. 此核交联胶束在254 nm紫外光照射下则会发生解交联反应. 采用尼罗红作为模型药物, 将其装载到超支化星形聚合物胶束中, 研究了不同条件下的药物释放行为.     

Synthesis and characters of hyperbranched poly(vinyl acetate) by RAFT polymeraztion

Reversible addition-fragmentation chain transfer (RAFT) polymerization of VAc in the presence of ECTVA, which capable of both reversible chain transferable through a xanthate moiety and propagation via a vinyl group, led to highly branched copolymers by a method analogous to self-condensing vinyl polymerization (SCVP). The ECTVA acted as a vinyl acetate AB^∗ inimer. It was copolymerized with vinyl acetate (VAc) in ratios selected to tune the distribution and length of branches of resulting hyperbranched poly(vinyl acetate). The degree of branching increased with chain ECTVA concentration, as confirmed by NMR spectroscopy. The polymer structure was characterized via MALDI–TOF. Retention of the xanthate compound during the polymerization was evidenced by successful chain extension of a branched (PVAc) macroCTA by RAFT polymerization. The branched PVAc led to better dissolution as compared to linear PVAc, an effect attributed primarily to an increased contribution of end groups.