| In this paper, Controlled/"living"photopolymerization of n-Butyl methacrylate (n-BMA) mediated by nitroxide and hindered amine derivatives has been performed in the three different types of microemulsions. The controlled mechanism and reaction kinetics of photo-induced free radical polymerization of n-BMA in microemulsion were further studied. The main work and conclusions as following:(1) The phase diagrams of n-BMA/n-butanol / sodium dodecyl sulfate (SDS)-H2O system, n-BMA/n-pentanol/SDS-H2O system, n-BMA/CTAB/H2O system and n-BMA/n-butanol /CTAB-H2O system were described by visual and conductivity method. The surfactant such as SDS is responsible for the stability of the latex by preventing coagulation between particles.The variation in structure of microemulsion was measured by conductometer, the results showed that the conductivity of microemulsion changed with increasing the aqueous phase, and indicated that the system changed from W/O microemulsion to bicontinuous microemulsion, and finally reached to O/W microemulsion. The particles analysis showed that there was no change in number orders between particals of n-BMA microemulsion and latex particals after photopolymerization.(2) After selecting experiment conditions of using Irgacure184 as an initiator in the ambient temperature, because of the low monomer concentration and the high emulsifier concentration, the chain pragation reaction was prevented in the O/W microemulsion. Therefore, whether using SDS as emulsifier or CTAB, the performance of controlled by HO-TEMPO on the reaction kinetics of n-BMA photopolymerization is not ideal. The convertion is too low, molecular weight is too small, moreover the polydispersity index (PDI =Mw/Mn) is too high.When in the W/O microemulsion with SDS as an emulsifier, the monomer concentration was increased so that the conversion became high in the photopolymerization system of n-BMA mediated by HO-TEMPO. Meanwhile, the conversation vs. time and Ln([M0]/[M]) vs. time were almost liner respectively, molecular weight increased linearly with the increasing of conversation also, moreover the PDI is small (the lowest is 1.5), the HO-TEMPO bring a good result of controlling effect of n-BMA photopolymerization. When using CTAB as an emulsifier, we use toluene as co-oil phase in order to increase the monomer concentration. When it was mediated by TMP/HO-TEMPO, especially when the molar ratio of TMP/HO-TEMPO was 2.0, the photopolymerization of n-BMA in the microemulsion was controlled. Because the TMP in situ photo-induced chemically oxidated into nitroxide which consumed the oxygen in the system, and TMP had a co-mediator effect. It was found that the Ln([M0]/[M]) vs. time and Mn of n-BMA homopolymer increased linearly respectively and relatively narrow PDI (1.7-1.4) in the reverse microemulsionr .In the biocontinuous microemulsion mediated by HO-TEMPO, the monomer concentration was lower than reverse microemulsion, the convertion decreased when SDS using as emulsifier. The results were shown that obtained the n-BMA homopolymers molecular weight were arsy-varsy, although plots of number-average molecular weight vs. conversion and Ln([M0]/[M]) vs. time were almost liner respectively. So the HO-TEMPO brought limited controlling effect to biocontinuous microemulsion when SDS using as emulsifier. While CTAB was used as emulsifier, the convertion vs. time and Ln([M0]/[M]) vs. time were almost liner respectively, molecular weight increased linearly with the increasing of conversation also, moreover the PDI is small (the lowest is 1.5), the photopolymerization of n-BMA using CTAB as an emulsifier in the biocontinuous microemulsion was well controlled.(3)By use of dynamic light scatter equipment, the particles sizes showed that there was no change between microemulsion before polymerization and after. Based on stable polymerization, the morphylogy of the n-BMA homopolymers in the biocontinuous microemulsion polymerization was characterized by environmental scanning electron microscope (SEM). It indicated that Open-cell porous polymers with a bicontinuous structure were obtained by the photopolymerization of n-BMA in the microemulsions. |
