Crosslinking in solution

A series of novel styrene- and siloxane-based silanol polymers and copolymers were synthesized by a selective oxidation of the Si—H bond with a dimethyldioxirane solution in acetone from corresponding precursor polymers. The conversion of the Si—H to Si—OH in the polymer modification proceeded rapidly and selectively. The silanol polymers obtained in situ showed no tendency for self-condensation to form siloxane crosslinks in solution. Moreover, stable silanol polymers in the solid states were obtained by placing bulky substitute groups bonded directly to the silicon atom. It was found that the properties of these novel silanol polymers and copolymers depended largely on substituents bonded directly to the silicon atom and silanol composition in the copolymers as well. 

RrjtKE, A. M. Crosslinking in solution. Studies on cellulose acetate networks. Ph. D. Thesis, University Leiden 1961. 

Polyethylene oxide has been shown to be an excellent mucoadhesive polymer. Low levels of polyethylene oxide are effective thickeners, although alcohol is usually added to water-based formulations to provide improved viscosity stability see Table II. Polyethylene oxide films demonstrate good lubricity when wet. This property has been utilized in the development of coatings for medical devices. Polyethylene oxide can be radiation crosslinked in solution to produce a hydrogel that can be used in wound care applications. 

Section 7.5. Networks with modulus lower than the plateau modulus can also be prepared by crosslinking chains in solution and then removing the solvent, because fewer entanglements are trapped by crosslinking in solution. ... 

Polymeric gels are crosslinked polymers swollen in a liquid. The polymer serves as a matrix to hold the liquid together, while the liquid inside the gel allows free diffusion of some solute molecules. Polymeric gels can be prepared from either monomeric or polymeric precursors dissolved in a solvent. However, the most commonly used method is the free-radical crosslinking copolymerization of a monovinyl monomer with a divinyl monomer (crosslinker) in solution. In the... 

Rijke, A. M. Prins, W., The Swelling of Cellulose Acetate Networks Obtained by Crosslinking in Solution. J. Polym. Sci. 1962, 59,171-190. 

In a somewhat related network problem, Meissner and Klier derived an equation to express the behavior of supercoiled networks. Such materials may be prepared by polymerization and/or crosslinking in solution, and evaporation of the solvent. 

Polymers that crosslink in the solid state can also be used in solution. Particularly in water, the hydrogen abstraction created by reactive POH radical due to the decomposed water indirectly yields polymer radicals [12], The rate of crosslinking in solution is greater than in solids due to a high mobility of the generated polymer free radicals. 

As discussed previously, equilibrium swelling is reached when the net gel swelling pressure is zero. For a non-ionic gel prepared in the bulk state, the Flory-Rehner theory represents total gel swelling pressure as the sum of the mixing and elastic pressures [46]. Total gel swelling pressure may be written as follows for networks crosslinked in solution, by combination of equations (2) and (4) [13] ... 

Block copolymers are useful in many applications where a number of different polymers are connected together to yield a material with hybrid properties. For example, thermoplastic elastomers are block copolymers containing a rubbery matrix (polybutadiene or polyisoprene) containing glassy hard domains (often polystyrene). The block copolymer, a kind of polymer alloy, behaves as a rubber at ambient conditions, but can be moulded at high temperatures due to the presence of the glassy domains that act as physical crosslinks. In solution, attachment of a water soluble polymer to an insoluble polymer leads to the formation of micelles in amphiphilic block copolymers. The presence of micelles leads to structural and flow characteristics of the polymer in solution that differ from either parent polymer. 

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