•OH对聚二甲基硅氧烷乳液辐射效应的影响

通过凝胶和溶胶分析与分子量测定的方法，研究了不同体系下，^•OH对PDMS乳液γ辐射效应的影响. 结果表明，^•OH不仅可引发聚二甲基硅氧烷的分子间交联，也能促进其降解. 对于纯PDMS乳液，在所研究的剂量范围内，^•OH对其辐射交联行为影响较小. 但若体系中加入H2O2、KIO4 和 N2O这些提高^•OH生成产额的添加剂时，^•OH对PDMS的促降解作用会随着吸收剂量增加而表现更明显，导致凝胶含量与纯乳液辐照情况相比下降较多. 即使加入交联剂-三羟甲基丙烷三甲基丙烯酸酯（TMPTMA），在过量的^•OH存在下，当吸收剂量大于40 kGy以上时，TMPTMA不仅没有提高交联度，反而会与^•OH协同，使PDMS的凝胶含量下降更显著，同时产生更多的小分子聚合物，并使PDMS的平均分子量分布变窄. 这可能是由于交联剂首先与^•OH作用，形成的产物会加快PDMS的降解.

Influence of Radicals on the Radiation Effect of Polydimethylsiloxane Latex

By measuring the gel fraction and GPC spectra of irradiated polydimethylsiloxane (PDMS) samples, the radiation effect of PDMS in latex form was investigated. Results showed that the ^•OH radical could not only initiate the radiation crosslinking of PDMS latex, but also accelerate the scission of PDMS molecular chain. For the PDMS latex without additives, the effect of ^•OH on the crosslinking behavior is not obvious. However, the addition of H2O2 or KIO4 or N2O which could increase the concentration of ^•OH would enhance the radiation degradation of PDMS. Moreover, with the increase of absorbed dose, the degradation is more predominant to lead to the drop of gel fraction. Particularly, in the presence of crosslinking sensitizer-trimethylol propane trimethacrylate (TMPTMA), when the dose was above 40 kGy, the excess ^•OH radical accelerated remarkably the degradation of PDMS chain which resulted in the narrow polydispersity of molecular weight and increase in content of PDMS with low molecular weight, and decrease of gel fraction, comparing with those of irradiated PDMS latex without TMPTMA. This suggested that the synergetic interaction perhaps existed between TMPTMA and excess ^•OH radical. This might be attributed to that the ^•OH radicals react with TMPTMA firstly, the resulted product might accelerate the degradation of PDMS.