Research On Reaction Kinetics Of Controlled/Living Photopolymerization Of Acrylate Monomer In Microemulsion

Controlled/living polymerization has the obvious advantage in the field of synthesis of block copolymers, which could gain well-defined expected copolymer. Recently, increasing attention has been paid to it by home and overseas scholars. In this paper, a new bifunctional initiator was synthesized firstly. Then, Controlled/living photopolymerization of methyl methacrylate (MMA) in anionic reverse microemulsions and n-butyl methacrylate (n-BMA) in anionic normal microemulsions mediated by 2,2,6,6-tetramethyl-1-piperidine-1-oxyl(TEMPO)/2,2,6,6-tetramethyl-4-piperidinol(TMP) have been performed. The controlled mechanism and the reaction kinetics of the two systems were further studied, and the products prepared from above two processes were characterized. The main work and conclusions as following:(1) A noval bifunctional initiator (HMPP-Br) was synthesized by the condensation of 2-bromoisbutyryl bromide (BSB) with Darocur1173 (2-hydroxy-2-methyl-propio-phenone, HMPP) in methylene dichloride (CH2Cl2), with pyridine as a catalyst. The structure and reactivity of the product has been characterized by element analysis, FTIR, 1H NMR and UV-Visible spectra. Especially, the results show that the wavelength of the absorption peak of HMPP-Br is almost as same as Darocur1173, which was important to the photopolymerization in the next step.(2) The phase diagrams of MMA (n-BMA)/n-butanol/SDS-H2O system were described by visual and conductivity method. The variation in the phase bounder of microemulsion was measured by conductometer. The results show that the conductivity of microemulsion changed with increasing the aqueous phase, and indicated that the phase shift changed from W/O microemulsion through bicontinuous microemulsion to O/W microemulsion.(3) After selecting excellent experimental conditions, Controlled radical photopolymerization (CRPP) of n-BMA and MMA mediated by TEMPO/TMP have been carried out in anionic W/O microemulsion respecrively, using HMPP-Br as an initiator. The reaction kinetics of polymerization was studied. The results show that when it was mediated by TEMPO/TMP, the photopolymerization of n-BMA and MMA in microemulsion was to be kinetic controlled. It was found that plots of number-average molecular weight vs. conversion and ln([M]0/[M]) vs. time were liner respectively, and obtained the n-BMA and MMA ho mo polymers exhibited relatively narrow molecular weight distributions respectively, even until the conversion was up. This shows that TEMPO combined with TMP used as a mediator was evidently available.(4) Poly(Methyl Methacrylate)-block-Polystyrene(PMMA-b-PS) diblock copolymer was prepared by atom-transfer radical polymerization (ATRP) technique in cyclohexanone, with the macro initiator PMMA-Br as an initiator, CuBr/2,2-bipyridine as a catalyst. The polymers were characterized by GPC,1H NMR, FTIR and TGA. The TGA spectra of polymers, there were two decomposition peaks, thus supporting the polymer (PMMA-b-PS) was indeed a single two-block copolymer structure.