| Popis: |
Methacrylate-terminated poly(dimethylsiloxane) (PDMS) macromonomers have been obtained through a flexible synthetic method which has been tailored into an efficient 1 pot, 2 stage reaction. Linear and star-shaped analogues have been synthesised and 3 molecular weights of each architecture were produced for use in subsequent curing investigations. The PDMS macromonomers were photo cured into films by exposure to UV irra- diation in the presence of a free-radical initiator. A curing time study was carried out and the rheological properties, swelling ratio, Young's modulus, surface tack and macroscopic extension of the cured films were investigated. At short irradiation times, samples were sensitive to irradiation time and an increase in exposure produced a signif- icantly more solid-like film. However, after longer irradiation times, the film properties reached a plateau and films did not become significantly more solid-like despite further irradiation. Ideal network models are proposed which support the observation that the cured film properties were strongly affected by the macromonomer molecular weight. Low molecular weight macromonomers produced densely cross-linked films which were hard, elastomeric solids. Films formed from medium molecular weight macromonomers were softer materials with tacky surfaces, and films formed from the highest molecular weight were softer still and some samples exhibited viscous flow. Introducing branching into the macromonomers decreased the irradiation time re- quired to form a cohesive film. Increasing the degree of macromonomer branching increased the solid-like nature of the film in comparison to those formed from linear species, although this did not outweigh the effect of macromonomer molecular weight. The materials investigated in this study may have potential for use as non-degradable, curable materials in medical applications and have scope for in vivo curing. |
