Anisotropic cellular structures from semi-crystalline polymer templates

We report an investigation to determine the effect of an anisotropic semi-crystalline template on the resulting cell morphology of microcellular polymeric foams generated in these materials. Poly(ethylene terephthalate) (PET)-polystyrene (PS) composite foams are prepared by using supercritical carbon dioxide (scCO₂) not only as a foaming agent but also as a transport medium of styrene and initiator into a biaxially-oriented PET templating film. The composite foam so obtained demonstrates a highly interpenetrating network verified by a single Tg of 98°C. Substrate orientation is observed not to dictate the cell formation; however highly anisotropic swelling and a shape-templating phenomenon is observed, with the most significant dimension change in the thickness of the film. Introducing confinement in the direction of maximum dimension change is found to introduce a highly anisotropic lamellar cell architecture.     

Determination of aromatic amines in aqueous extracts of polyurethane foam using hydrophilic interaction liquid chromatography and mass spectrometry

A method is presented for the determination of aromatic amines in aqueous extracts of polyurethane (PUR) foam. The method is based on the extraction of PUR foam using aqueous acetic acid (0.1%, w/v) followed by determination of extracted aromatic amines using hydrophilic interaction liquid chromatography (HILIC) and tandem mass spectrometry (MS/MS) with positive electrospray ionisation. The injections of volumes up to 5 μL of aqueous solutions were made possible by on-column focusing with partially filled loop injections. The fragmentation patterns for 2,4- and 2,6-toluene diamine (TDA) and 4,4′-methylene dianiline (MDA) were clarified by performing a hydrogen-deuterium exchange study.TDA and MDA were determined using trideuterated 2,4- and 2,6-TDA and dideuterated 4,4′-MDA as internal standards. Linear calibration graphs were obtained over the range 0.025-0.5 μg mL⁻¹ with correlation coefficients >0.996 and the instrumental detection limit for each compound was <50 fmol. The stability of the amines was influenced by the matrix, so their concentrations decreased over time.Agreement was observed between the results of analyses of PUR foam extracts by HILIC-MS/MS and results obtained by ethyl chloroformate derivatisation and reversed phase (RP) liquid chromatography-mass spectrometry (LC-MS/MS).TDA was observed to be unstable in extracts of foam but not in pure solutions.     

Fabrication of porous 3-D structure from poly(l-lactide)-based nano-composite foams. Effect of foam structure on enzymatic degradation

To understand the effect of the foam structure on the enzymatic degradation and porous structure development, we have examined the enzymatic degradation of a poly(l-lactide) (PLLA)-based nano-composite foam having different cell density (microcellular and nanocellular), using proteinase-K as a degrading agent at 37 °C. The surface and cross-sectional morphologies of the foam recovered after enzymatic hydrolysis for different intervals were investigated by using scanning electron microscopic and mercury porosimetric analyses. The fabrication of porous three-dimensional structure for tissue engineering scaffolds and the degradation performance in nano-composite foams were discussed.