No abstract

SynopsisSynthesis of novel triblock, polycaprolactone-b-polydimethylsiloxane (PDMS) and poly(2ethyl-oxazoline)-b-PDMS copolymers were demonstrated. These materials were obtained via the ring-opening polymerization of c-caprolactone or 2-ethyl-2-oxazoline monomers by using organofunctionally terminated PDMS oligomers as initiators and comonomers. Segment molecular weights in these copolymers were varied over a wide range between lo00 and 2oooO g/mol and the formation of copolymers with desired backbone compositions were monitored by 'H-NMR spectroscopy and GPC. DSC and TMA studies showed the formation of two phase morphologies with PDMS (Tg, -120°C) and polycaprolactone (Tm, 50-60°C) or poly(2-ethyl-2-oxazoline) (Tgr 40-60°C) transitions respectively. The use of polycaprolactone-b-PDMS copolymers as surface modifying additives in polymer blends were also investigated. When these copolymers were blended at low levels (0.25-10.0% by weight) with various commercial resins such as, polyurethanes, PVC, PMMA, and PET, the resulting systems displayed silicone-like, hydrophobic surface properties, as determined by critical surface tension measureIl,ents or water contact angles. The effect of siloxane content, block length, base polymer type and morphology on the resulting surfaces are discussed.

The block microstructure of a block copolymer ionomer, lightly sulfonated poly(6-styrene-6-(r-ethylene-co-r-butylene)-6-styrene) (S-SEBS), was investigated by small angle X-ray scattering. Sulfonation level was varied from 0 to 12 mol % of the polystyrene blocks and the sulfonic acid derivatives and Na and Zn salts were studied. Compression molded samples had a deformed spherical domain structure, and the extent of microphase separation was influenced by ionic aggregation that occurred in the sulfonated polystyrene domains. The extent of microphase separation decreased with increasing sulfonation level and with increasing strength of the ionic interactions, i.e., Na+ > Zn2+ > H+. Solution-cast samples exhibited a lamellar microstructure for the Zn salts and a spherical microstructure for the Na salts. Samples swollen with a paraffinic oil that plasticizes the rubber phase exhibited a spherical domain structure with a cubic arrangement of the domains. The development of microphase separation, however, decreased with increasing ionic strength of the ion dipoles.

No abstract

The separation of hazardous metals from contaminated sources is commonly achieved with ion-exchange resins. The resins have a high surface area decorated with many ion-exchange sites and thus a high sorption capacity for the analyte of interest. However, these sites are primarily accessed by diffusion which limits the throughput and quality of the separation. Reported herein is a study of monolithic polyHIPE foam columns surface-grafted with a brush of polymer containing ion-exchange functionality for the separation of Pu. It was found that the loading curves of the foam material are steeper than a similarly scaled resin-based column, and the elution profiles of the foams were narrower than the resin, generating more concentrated eluate relative to the amount of Pu loaded onto the foam columns. On a gravimetric basis, the foams had a similar or greater Pu capacity than the resin with fewer ion-exchange sites per unit mass. These characteristics are mainly due to the convective mass transport which dominates the separation in the polyHIPE materials, suggesting that these materials may be useful for more efficient hazardous metal separations.