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Atom Transfer Radical Polymerization Of Methyl Methacrylate And Styrene Under Microwave Irradiation And Conventional Heating

Posted on:2004-11-25Degree:DoctorType:Dissertation
Country:ChinaCandidate:Z P ChengFull Text:PDF
GTID:1101360122465555Subject:Organic Chemistry
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In this thesis, we first tried to use pulsed microwave irradiation (PMI) and microwave irradiation (MI) in atom transfer radical polymerization (AIKP) of methyl methacrylate (MMA) . The following homogeneous solution ATRPs of MMA in N, N-dimethylformamide (DMF) were successfully carried out under PMI and MI at 69@, respectively. For PMI: (1) the reverse ATRP (RATRP) of MMA with the initiating system of azobisisobutyroaitrile (AIBN)/CuBr2/tetramethylethylenediamine (TMEDA); (2) the ATRP of MMA with the initiating system of ethyl 2-bromobutyrate (EBB)/CuCl/ N,N,N', N" , N" -pentamethyldiethylenetriamine (PMDETA). For MI: (1) the ATRP of MMA with low concentration of initiating system of EBB/CuCl/PMDETA; (2) the RATRP of MMA with the initiating system of AIBN/FeCl3/triphenylphosphine (PPh3). In addition, the following systems were also successfully carried out under conventional heating (CH) process. (1) the living/controlled radical autopolymerization of styrene in the presence of CuCl2and 2, 2' -bipyridine (bpy); (2) the RATRP of MMA with the initiating system of AIBN/CuBr2/PMDETA; (3) the synthesis of difunctional ABA-type triblock copolymers and gels of PBA-b-PS-b-PBA and PS-b-PBA-b-PS with a , a '-dichloride-xylene/CuBr/bpy as an initiating system.It was found that plots of ln ([M]o/[M]) vs. time and molecular weight evolution vs. conversion showed a linear dependence by the kinetic studies of (R)ATRPs of MMA under PMI and MI, respectively, and that the "living'Vcontrolled characters of the polymerization systems were not changed under PMI or MI by a series of characterizations for polymersobtained (i.e., chain extension, analysis of end-groups and stereochemistry of PMMA). Under identical polymerization conditions, the apparent constant of propagation (kpapp) under PMI or MI were 1.5-12.8 times larger than that under CH, indicating a significantly increase of the polymerization rates whether under PMI or under MI. Furthermore, the apparent initiator efficiencies under PMI or MI were improved but the molecular weight distributions kept quite narrow (1.1 ~ 1.5), indicating that the control over molecular weights whether under PMI or under MI were also improved. It was noted that PMI or MI could greatly lower the polymerization temperature as well as the amount of catalyst if the same polymerization rate as CH was kept. For example, for the ATRPs of MMA under PMIand CH with the initiating system of EBB/CuCl/PMDETA (Conditions: MMA/DMF = 2/l(v/v); pulse power = 80kW, mean power = 12W; polymerization temperature = 69℃; [MMA]0/[EBB]0/[CuCl]0/[PMDETA]0 = 400/1/n/0.89n (n = 1, 3).), kpapp under CH was 1.15 x 10-5s-1 (n = 1); while the one under PMI was 8.20X 10-5s-1 (n = 1), being 7.1 times larger than that of the former, and almost double that (4.42 X 10-5s-1 for n = 3) under CH using three times concentration of catalyst. Furthermore, when [MMA]0/[EBB]0/[CuCl]0/[PMDETA]0 = 400/1/1/1.78, even if the polymerization temperature was as low as 69@, the kpapp (30.03 X 10-5s-1) under PMI increased by 16% than that (25.90x10-5s-1) under CH at 110@.The homogeneous RATRP of MMA, using AIBN/CuBr2/PMDETA as initiation system, could be easily carried out in DMF (25%, v/v) under CH at 69@. Plots of ln ([M]0/[M]) vs. time and molecular weight evolution vs. conversion showed a linear dependence. The molecular weight distributions kept quite narrow (1.07-1.5), but the initiator efficiencies were very low (generally below 0.5), indicative of a poor control of molecular weight. RATRP exhibited inverse first-order kinetics with respect to the initial copper(II) concentration, however, the polymerization kinetics were not first-order (0.84) with respect to the initial initiator concentration.The bulk autopolymerization of styrene (St) was successfully conducted in the presence of CuCl2 and bpy at 110@ and 130@, respectively. It was found that this polymerization was a "living"/controlled radical polymerization. The resulting Mns linearly increased with conversion, and PDIs were very narrow (below 1.5). The polymeriza...
Keywords/Search Tags:pulsed microwave irradiation (PMI), microwave irradiation (MI), atom transfer radical polymerization (ATRP), methyl methacrylate (MMA), styrene (St), gels, living polymerization
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