Spinodal phase separation in semi-interpenetrating polymer networks - polystyrene-cross-polymethacrylate

Morphology control in semi-interpenetrating polymer networks has been achieved by means of a two-step process, separating morphology formation and polymerization/crosslinking. Phase textures formed during spinodal liquid/liquid demixing of a solution of atactic polystyrene in methacrylate monomers were arrested by thermoreversible gelation of the polymer-rich phase as this phase passed its glass transition temperature. The phase separated structure was permanently stabilized by low-temperature crosslinking ultraviolet (UV) polymerization of the methacrylate monomer, and studied by transmission electron microscopy. Thus, it was directly observed how the initial demixing process depended on the initial viscosity of the polymer solution and the mode of quenching. Arrest of the earliest stage of spinodal demixing resulted in separated domains of 0.05-0.08 m thickness, which were separated by a distance of the spinodal wavelength . A cocontinuous network only developed in a relatively late stage of demixing

Influence of the bulk and surface morphology on adhesion of polystyrene-inter-poly-cross-2-ethylhexyl-methacrylate films and particles

The adhesion behavior of semi-interpenetrating polymer networks (semi-IPNs) of linear polystyrene (PS) in crosslinked poly-2-ethylhexylmethacrylate (EHMA) was studied by variation of the bulk and surface morphology, i.e., domain size, continuity, and concentration in the domains. Semi-IPNs were prepared by liquid-liquid demixing upon cooling of a homogeneous solution of PS in methacrylate monomer, followed by gelation of the PS-rich phase and UV polymerization of the methacrylate resin. Welding of films allowed the preparation of larger objects provided that (1) the samples were phase separated to a high degree and contained domains with a high PS concentration (>90%) and (2) polystyrene was present at the interface. For semi-IPN films, a linear dependence of the adhesion strength on the (crack healing time)1/4 was obtained. Based on these considerations, a process was developed to obtain melt-processable semi-IPN particles, by quenching droplets of the polymer solution into a cold liquid. These particles obtained a PS-rich skin layer and showed good adhesion after blending with a thermoplast

Spinodal phase separation in semi-interpenetrating polymer networks—polystyrene-cross-polymethacrylate

Morphology control in semi-interpenetrating polymer networks has been achieved by means of a two-step process, separating morphology formation and polymerization/crosslinking. Phase textures formed during spinodal liquid/liquid demixing of a solution of atactic polystyrene in methacrylate monomers were arrested by thermoreversible gelation of the polymer-rich phase as this phase passed its glass transition temperature. The phase separated structure was permanently stabilized by low-temperature crosslinking ultraviolet (UV) polymerization of the methacrylate monomer, and studied by transmission electron microscopy. Thus, it was directly observed how the initial demixing process depended on the initial viscosity of the polymer solution and the mode of quenching. Arrest of the earliest stage of spinodal demixing resulted in separated domains of 0.05-0.08 m thickness, which were separated by a distance of the spinodal wavelength . A cocontinuous network only developed in a relatively late stage of demixing

Glass transition temperatures of microphase-separated semi-interpenetrating polymer networks of polystyrene-inter-poly(cross-2-ethylhexyl methacrylate)

The glass transition temperature of semi-interpenetrating polymer networks (semi-IPNs) of atactic polystyrene (PS) in crosslinked methacrylates was studied by systematic variation of the morphology, that is domain size, continuity and concentration in the domains. Semi-IPNs were prepared from homogeneous polymer solutions in a two-step process, of liquid-liquid demixing upon cooling followed by gelation, and subsequent ultra-violet polymerization. Semi-IPNs with very little developed phase separation could be obtained, which exhibited optical transparency and a mechanical behaviour similar to that expected for corresponding homogeneous systems. A low PS concentration inside the domains indicated that these domains consisted of only an interphase layer. Samples that were phase separated to a larger extent showed normal two-phase behaviour

Spinodal phase separation in semi-interpenetrating networks - polystyrene-cross-polymethyl-methacrylate

Morphology control in semi-interpenetrating polymer networks has been achieved by means of a two-step process, separating morphology formation and polymerization/crosslinking. Phase textures formed during spinodal liquid/liquid demixing of a solution of atactic polystyrene in methacrylate monomers were arrested by thermoreversible gelation of the polymer-rich phase as this phase passed its glass transition temperature. The phase separated structure was permanently stabilized by low-temperature crosslinking ultraviolet (UV) polymerization of the methacrylate monomer, and studied by transmission electron microscopy. Thus, it was directly observed how the initial demixing process depended on the initial viscosity of the polymer solution and the mode of quenching. Arrest of the earliest stage of spinodal demixing resulted in separated domains of 0.05-0.08 m thickness, which were separated by a distance of the spinodal wavelength . A cocontinuous network only developed in a relatively late stage of demixing

Processing and characterization of biodegradable soy plastics : effects of crosslinking with glyoxal and thermal treatment

Processing and modification routes to produce and to improve properties of biodegradable plastics from soy isolate were studied. Soy isolate, acid-treated and crosslinked soy were subsequently compounded, extruded, and injection molded. Acetic acid and glyoxal were examined concerning their suitability for acid treating and crosslinking of soy, and their effect on the final properties of the obtained materials. Heat treatment was also used as a possible methodology to crosslink the protein structure. The molded specimens were tested in terms of their tensile properties and solubility at different pHs, and were also evaluated for the degree of crosslinking and molecular weight distributions. The obtained plastics were rigid and brittle with stiffness ranging from 1436 MPa for soy, to 1229 MPa for glyoxal crosslinked soy, up to 2698 MPa for heat-treated soy. The differences in stiffness were discussed in terms of the crosslinking efficiency and spatial distribution. The solubility profiles were studied as a function of the pH of the immersion solutions and the crosslinking degree of each material. A reduction in protein solubility with decreasing pH was observed, with a minimum between pH 4 and 5 and a resolubilization of the protein at pHs lower than pH 4 and greater than 8. Higher levels of crosslinking resulted in a decrease of the solubility and an aggregation of the protein molecules. The soy plastics proved to be very versatile materials with potential to be used in applications where quite demanding performances are expected, such as in the biomedical field