Synthesis Of Polymers With Functional Chain-side Or Chain-end Via "Living"/controlled Radical Polymerizations

"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 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.