Polydimethylsiloxanes kinetics

Koberstein and coworkers121 have examined the effects of a polydimethylsiloxane-polystyrene (PDMS-PS) block copolymer on the interfacial tensions of blends of PDMS and polystyrene. As little as 0.002 wt% of the copolymer, added to the siloxane phase, was sufficient to lower the interfacial tension by 82% in the case of a blend of polystyrene (Afn = 4,000) and PDMS (Mn = 4,500). No further reduction in interfacial tension was observed at higher copolymer levels due to micelle formation. Riess122 has polymerized styrene in the presence of a silicon oil and a polydimethylsiloxane-polystyrene block copolymer to obtain a polystyrene in which 0.1-1 pm droplets of silicone oil are dispersed. This material displayed a lowered coefficient of kinetic friction on steel compared to pure polystyrene. 

FichetO et al. (2005) Polydimethylsiloxane-cellulose acetate butyrate IPN synthesis and kinetic study, Part I. Polymer 46 37-47... 

In our studies of the polymerization of cyclic siloxane monomers we observed anomalies in the kinetics of the process and in the viscosity changes of the medium. The growing polydimethylsiloxane chain ends were found to associate... 

When polydimethylsiloxane fluids are irradiated in the presence of anthracene, the additive is incorporated into the macromolecular system [365]. The kinetics of anthracene disappearance has been studied and interpreted by Jenkins [365] in terms of a theory assuming that the active centres (probably radicals) are produced at random and that they disappear either by reacting with the additive or with neutral molecules, but not with each other. 

The most important class of solid-state enzyme mimics is based on zeolites. Zeolites are solid materials composed of Si04 or AIO4 tetrahedra linked at their corners, affording a three-dimensional network with small pores of molecular dimensions. They possess a unique feature of a strictly uniform pore diameter. In particular, zeolites with encapsulated metal complexes are used as inimics of cytochrome P-450.An efficient enzyme mimic was obtained by encapsulating an iron phthalocyanine complex into crystals of zeolite Y, which were, in turn, embedded into a polydimethylsiloxane membrane acting as a mimic of the phospholipid membrane.With t-butylhydroperoxide as the oxidant, the system hydroxyl-ates alkanes at room temperature with rates comparable to those for the enzyme. It shows similar selectivity (preference oxidation of tertiary C-H bonds) and a large kinetic isotope effect of nine. 

Liu, K. and Kiran, E. (1999) Kinetics of pressure-induced phase separation (PIPS) in solutions of polydimethylsiloxane in supercritical carbon dioxide Crossover from nucleation and growth to spinodal decomposition. J. Supercrit. Fluids, 16, 59-79. 

Fichet, O. Vidal, F. Laskar, J. Teyssie, D., Polydimethylsiloxane-Cellulose Acetate Butyrate Interpenetrating Polymer Networks Synthesis and Kinetic Study. Part I. Polymer 2005,46, 37-47. 

Thomas et al. [16] used CSLM to observe in situ the formation of polyamide membranes and the measurements were used to study polymer precipitation kinetics. Turner and Cheng [17] applied CSLM and hydrophilic fluorescent probes of varying molecular weights to image the size distribution of poly(methacrylic acid) (PMAA) hydrogel domains in polydimethylsiloxane (PDMS)-PMAA interpenetrating polymer networks. The combination of CSLM with AFM, SEM and X-ray spectroscopy allowed characterization of the structure of stimuli-responsive polymeric composite membranes [18]. 

Addad, J.P.C., Dujourdy, L. Silica concentration dependence of the kinetics of polydimethylsiloxane adsorption on aggregates. Polym. Bull. 41, 253 (1998)... 

Figure 5 Kinetically controlled decal transfer printing, (a) Schematic drawing of the process used to transfer microfabricated structures from a donor substrate to a polydimethylsiloxane (PDMS) stamp, and then from the PDMS stamp to a receiver substrate, (b and c) scanning electron microscope (SEM) images oftwo-and three-dimensional structures fabricated by this process. Reproduced with permission from MeitI, M. A. Zhu, Z. T. Kumar, V. etal. Nat. Mater. 2006, 5,33-38. Copyright 2006, Nature Publishing Group.

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