High internal phase emulsion (HIPE) copolymer and interpenetrating network foams were prepared from 2‐ethylhexyl acrylate (EHA), styrene (S) and divinylbenzene (DVB) using a unique process. The morphologies, thermal properties and dynamic and static mechanical properties of these foams were investigated. The glass transition temperatures and damping properties of the EHA/S copolymer foams vary with its composition. IPN foams with very broad tan 5 peaks were obtained. The damping properties of IPN foams were tailored through changing copolymer composition and monomer composition. The IPN foams based on a copolymer foam and styrene had a broader tan δ peak, a higher glass transition temperature and a higher modulus than tne copolymer foams of similar overall styrene contents. It is therefore possible to prepare novel damping foams based on polyHIPE foams through the synthesis of interpenetrating polymer networks.
The recognition that eye lenses in nature often employ a gradient refractive index to enhance the focusing power and to correct aberrations has motivated us to construct a synthetic lens using the layered concept encountered in biological lenses. The result is a highly flexible technology for the fabrication of gradient-refractive index lenses that is based on a method of polymer forced assembly. Polymeric nanolayered films with incremental differences in the refractive index are assembled according to a prescribed design and molded into the desired shape. The exceptional flexibility of the process lies in the wide range of lens shapes and index profiles that can be realized. A lens with any refractive index distribution can be achieved within the refractive index range of available coextrudable optical materials.
ABSTRACT:The synthesis and characterization of novel polymerized high internalphase emulsions (polyHIPE) materials are described. Homogeneous, highly porous, low-density, open-cell crosslinked copolymers were prepared by polymerizing the continuous phase of HIPE containing styrene and varying amounts of 2-ethylhexyl methacrylate. The glass transition temperatures (T g s) of the homopolymers were similar to the literature values, but the copolymer T g s were lower than expected. These results indicate that the copolymer composition is richer in 2-ethylhexyl methacrylate than the feed composition. The homopolymer moduli, calculated from the foam moduli, were similar to the literature values. The influence of composition and surface treatment on the water absorbed by the foams was investigated. For example, washing a polyHIPE based on poly(ethylhexyl acrylate) in water at 70°C increased water absorption because of the removal of the residual salt. Adding a fluorinated comonomer to the HIPE reduced hydrophilicity and, thus, water absorption.
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