Gelation techniques

Bamford et a l ° examined MAN polymerization (25 °C, DMSO) using the gelation technique (Section 5.2.2.2) and have estimated that termination occurs predominantly by disproportionation (kxJk]i = 1.86). This result is at variance with the model studies (Section 5.2.2.1.3). 

Ayrey el ai.165 suggested that transfer reactions may have led to erroneous conclusions being drawn in some of the earlier studies. They concluded that termination is almost exclusively by combination (25 °C, benzene). Bamford et at.m came to a similar conclusion using the gelation technique (25 °C, bulk) and determined that the polymerizations of higher acrylate esters also terminate predominantly by combination. 

Early reports37 157 167 suggested that termination during VAc polymerization involved predominantly disproportionation. However, these investigations did not adequately allow for the occurrence of transfer to monomer and/or polymer, which are extremely important during VAc polymerization (Sections 6.2.6.2 and 6.2.7.4 respectively). These problems were addressed by Bamford et who used the gelation technique (Section 5.2.2,2) to show that the predominant radical-radical termination mechanism is combination (25 °C). 

Park and Smith 170 attempted to allow for chain transfer in their examination of the termination mechanism during VC polymerization at 30 and 40 °C in chlorobenzene. They determined the initiator-derived ends in PVC prepared with radiolabeled AIBN and concluded that kjk = 3.0. However, questions have been raised regarding the reliability of these measurements.171 172 Atkinson et al.x72 applied the gelation technique (Section 5.2.2.2) to VC polymerization and proposed that termination involves predominantly combination. 

Temperatnre-indnced forming has several advantages when compared to conventional slip casting techniqnes. TIF ntilizes a gelation technique for consolidation, and in principle will prodnce green ceramic parts with less stress when compared... 

The ionotropic gelation technique utilizes other polymers to a lesser extent these are proteins such as gelatin and egg whites, semisynthetic polymers like hydroxyl propyl methyl cellulose, and synthetic polymers like polyacrylamides. 

The gelation technique allows to produce capsules bigger and denser, which degrade more slowly in simulated gastric fluids and provide better protection for the cells, compared to the capsules produced by spray drying. 

Ionotropic gelation technique combined with a spray drying method... 

For instance, Yadav and Ahuja prepared nanoparticles using gum cordia as the polymer and to evaluate them for ophthalmic delivery of fluconazole. A w/o/w emulsion containing fluconazole and gum cordia in aqueous phase, methylene chloride as the oily phase, and dioctyl sodium sulfosuccinate and polyvinyl alcohol as the primary and secondary emulsifiers, respectively, were cross-linked by the ionic gelation technique to produce a fluconazole-loaded nanoreservoir system. The formulation of nanoparticles was optimized using response surface methodology. Multiple response simultaneous optimizations using the desirability approach were used to find optimal experimental conditions. The optimal conditions were found to be concentrations of gum cordia (0.85%, w/v), di-octyl sodium sulfosuccinate (9.07%, w/v), and fluconazole (6.06%, w/v). On comparison of the optimized nanosuspension formulation with commercial formulation, it was found to provide comparable in vitro corneal permeability of... 

Wu, J., Liang, S., Dai, H. et al. (2010) Structure and properties of cellulose/chitin blended hydrogel membranes fabricated via a solution pre-gelation technique. Carbohydrate Polymers, 79(3), 677-684. 

Molecular weight distribution. End Group Analysis 13c NMR Gelation Technique Model Studies. 

Figure 27 Self-assembly of alkylated metallocycle 93 from 120° donor, and 91 from 120° acceptor, 92. SEM images of 93 after its subsequent ordering via gelation technique in (a) acetone/water (v/v 2/1) and (b) CH2CI2 (v/v 2/1) from an initial concentration of 5.0 X M. Adapted with permission from Ref. 14CC4231. Copyright 2014 Royai Society of Chemistry.

MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazoIium) assay. Saraei et al. [40] investigated alginate nanoparticles containing a model protein, bovine serum albumin (BSA), by the ionotropic gelation technique. The average particle size of the BSA-loaded alginate nanoparticles was 50nm, the zeta potential was -24 mV, and the polydispersity index was 0.36. 

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