【作者】 徐文健；

【导师】 朱秀林；

【作者基本信息】 苏州大学 ， 高分子化学与物理， 2005， 博士

【摘要】 “活性”/可控自由基聚合技术集自由基聚合与活性聚合的优点于一体,既可像自由基聚合那样进行本体、溶液、悬浮和乳液聚合,又可合成具有精致结构的分子量可控、分子量分布窄的聚合物,而且其聚合实施条件与传统自由基聚合相似,因此具有十分广阔的应用前景,引起了很多高分子化学研究者和产业界的关注。原子转移自由基聚合(Atom transfer radical polymerization, ATRP) 和氮氧稳定自由基聚合(Nitroxide-mediated radical polymerization, NMP)是“活性”/可控自由基聚合方法中研究报道较早,也是合成功能化聚合物中应用较多的两种方法。ATRP 不仅对常见单体如甲基丙烯酸甲酯(Methyl methacrylate, MMA),苯乙烯(Styrene, St) 等具有较好的控制能力,而且也适用于一些非常规结构的(甲基)丙烯酸酯类,通过在单体的酯基中引入特殊基团就可以合成侧链功能化的聚合物。另外,由于ATRP 引发剂的碎片会保留在聚合物链的末端,只要将含有特殊基团的化合物转变为ATRP 引发剂,就可以将特殊基团引入到聚合物链端,这样就提供了一条端基功能化的途径。相对于ATRP 而言,NMP 中的大多数调控稳定自由基对苯乙烯聚合时间较长,大分子引发剂扩链效果不佳,且只对苯乙烯和苯乙烯衍生物具有良好的调控效果,因此,NMP 实现聚合物链功能化主要是通过苯乙烯衍生物的形式来实现。本论文主要研究了以下内容:(1)以(甲基)丙烯酸长链酯为单体,在常规加热和微波辐射加热下,进行ATRP 研究,得到侧链具有长链烷基的聚合物。通过比较不同催化剂、溶剂、聚合温度等因素对聚合的影响,优化实验条件,并进一步考察其各自聚合行为;(2)分别合成了含甾类化合物结构的(甲基)丙烯酸酯和溴代丙酸甾烷酯,作为ATRP 单体和引发剂,聚合后可以得到侧链、端基含甾结构的聚合物,由于甾烷的手性特征,所得聚合物是旋光性聚合物。提供了一种简便的合成甾类旋光单体更多还原

【Abstract】 “Living”/controlled radical polymerization combines the advantages of free radical polymerization and living polymerization, it can be carried out in bulk, solution, suspension and also emulsion. On the same time, polymers with fine structures, predetermined molecular weights and narrow polydispersities can be synthesized through “living”/controlled radical polymerizations in the polymerization condition which is similar to that of traditional free radical polymerization. Atom transfer radical polymerization (ATRP) and nitroxide-mediated radical polymerization (NMP) are reported earlier among the methods of “living”/controlled radical polymerizations, and they are among the most usefully methods to synthesize functional polymers. ATRPs are not only used for the polymerizations of common monomers such as methyl methacrylate (MMA) and styrene (St), but also can be applied to the polymerizations of other (meth) acrylate monomers with different functional ester group to prepare functional polymers. In addition, if a functional compound can be used as an initiator for ATRP, polymer with a terminal functionality can be prepared, as the fragment of ATRP initiator will remain at the end of polymeric chains, which provides another way to prepare functional polymers. Compared to monomers used in ATRP, the common monomers that can be used in the polymerization mediated by stable free radicals are only styrene and its derivant. Furthermore, most of the styrene polymerizations mediated by stable free radicals have a relatively longer polymerization time. Our work in this thesis can be summarized as the following: (1) Under microwave irradiation and convention heating, the ATRPs of (meth)acrylate with long-chain alkyl ester groups were conducted to prepare the polymers with long alkyl side chain. Optimizations of the experimental conditions were done through comparing the effect of catalyst, initiator, solvent and temperature on polymerization; the behaviors of polymerization were further investigated. (2) (Meth) acrylate bearing pregnane-structure and bromo-propionic pregnane ester were synthesized, respectively. When they are used as the monomers and the initiators for ATRPs, polymers containing pregnane group at the side and end of chain were obtained. Due to the chiral structure of the pregnane group, polymers showed chiral characteristic. Therefore, a simple way to synthesize pregnane rotation monomers and polymers was provided. (3) Azobenzene initiator was synthesized for ATRPs of MMA and St to prepare polymers end-capped by azobenzene, the polymers showed strong UV absorbance. The ATRPs of azobenzene–containing methacrylate catalyzed by different system were conducted to compare the controlling ability of different systems. (4) Combining 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) and tetramethylthiuram disulfide (TMTD) as the initiator/mediator for polymerizations of styrene not only accelerate polymerization rate, but also decrease the polydispersity of polymers, furthermore, when with obtained polymer as the macroinitiator to initiate the polymeriations of styrene derivant, the polymers with narrower Mw/Mn and optical rotation characteristic are obtained. (5) The relationships between the initiator structure and the monomer structure are discussed by comparing the initiating ability of 2-bromo-propionic alkyl ester for polymerizations of (meth) acrylate and styrene. In summery, the following conclusions were made: (1) The rates of polymerization of butyl methacrylate and octyl acrylate under microwave irradiation were about 34 faster than those under convention heating, and polymerizations showed living characteristics. (2) When ethyl-2-bromopropionate (EBP) and ethyl-2-bromobutyrate (EBB) were used for the polymerizations of lauryl methacrylate (LMA) and hexadecyl acrylate (HDA), respectively, the rates of polymerization were 0.56 and 0.46 order with respect to the concentration of the initiator, which were much lower than 1.0 order of MMA reported by Matyjaszewski.When EBP and EBB were used for the polymerizations of LMA and HDA, respectively, in the presence of CuCl/ N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA), both of them showed good controlled ability, for example, 1.1<Mw/Mn<1.5. The initiator structure has less effect on polymerizations of LMA and HDA than on those of MMA and MA because the long-chain alkyl affects the activity of monomer. (3) By reacting the hydroxyl group in the structure of pregnane with (meth) acryloyl chloride, the monomers-bearing pregnane were synthesized and used to prepare the optical rotation polymers with controlled molecular weight and narrower polydispersity via ATRPs of the monomers-bearing pregnane. In the presence of CuBr/EBP, the EBP showed different initiation efficiency for the polymerizations of 20-(hydroxymethyl)-pregna-1, 4-dien-3-one acrylate (HPD-A), pregnenolone methacrylate (PR-MA) and β-cholestanol acrylate (CH-A). HPD-A as a monomer has smallest space steric hindrance of ester and its polymers had the narrowest Mw/Mn (in most cases, Mw/Mn<1.3). Though CH-A and PR-MA have similar ester structure, but the EBP showed a better controlling ability for acrylate(CH-A) than methacrylate (PR-MA), the Mw/Mn of the polymer of CH-A was narrower than that of PR-MA. The order of the apparent polymerization rates of the three monomers are kpapp(CH-A)> kpapp(HPD-A)> kpapp(PR-MA). In addition, we have measured the special rotation [α]D20 values of obtained polymers and found that the polymers have high special rotation [α]D20 values and the molecular weights of the polymers have no obvious effect on special rotation. (4) 20-(hydroxymethyl)-pregna-1, 4-dien-3-one 2-bromopropionate (HPD-Br) and estrone 2-bromopropionate (ES-Br) were used as rotation initiators for ATRPs of MMA and St, respectively, to prepare chain end-functional chiral polymers. The results showed that both HPD-Br and ES-Br were very efficient initiator for the ATRPs of St because the produced polymers had well-controlled molecular weights and narrow polydispersities (Mw/Mn<1.2). However, for the ATRPs of MMA, the initiation efficiency of both above mentioned initiators were rather lower (around 50 %), and the PMMAs had relatively broader polydispersities (Mw/Mn=1.4-1.5). The specific rotation [α]D20 values of obtained PMMA and PS were lower than those of theoriginal initiators, and decreased with the increase of molecular weights of the polymers. This result can be attributed to the lower contents of optically active moiety in these polymers. (5) 4-(4-phenylazo-phenylazo)-phenyl 2-bromopropionate (BPAzo) was used as an initiator for ATRPs of MMA and St in the presence of CuCl/PMDETA. The results showed that the polymerizations of MMA were well controlled in bulk and solvent with narrower molecular weight distributions. However, in the case of St, the rate of polymerization was slower and molecular weight distributions were broader. Reverse ATRPs of 4-(4ˊ-nitro-4″-oxy-azobenzene)butyl methacrylate (BMAzo) were conducted in the presence of AIBN /Cu[SCSN(C4H9)2]2. The polymerizations showed living feature with a polydispersity of less than 1.5.(6)In the presence of TMTD/TEMPO, the polymerizations of styrene showed a first order with respect to monomer concentration, the molecular weights with much narrow molecular weight distributions (Mw/Mn = 1.1-1.3) increased with conversion and were close to the theoretical values. The polymer obtained from TMTD/TEMPO/St (molar ratio 1/2/200) was used as the macroinitiator to initiate the polymerizations of styrene derivant bearing-pregnane optically active to prepare the polymers with narrower polydispersity and optical rotation.更多还原