Crosslinking, polymer film formation

Silanes can be polymerized into the backbone of a polymer during its synthesis [6]. Emulsion polymerization of methacryloxyalkyl or vinyl functional organosilanes has been shown to be a particularly useful method of incorporating a crosslinking silane into a waterborne system. Subsequent to reaction of the methacryl or vinyl functionality, the alkoxy groups are left available either to react with a substrate or filler, or to crosslink upon film formation. 

Crosslinking. Crosslinked polymer films allow swelling without dissolution. Since films of polymers are often prepared by casting linear polymers from solution, crosslinks are usually introduced after film formation. Incorporation of highly charged ions, such as ferricyanide automatically leads to crosslinking of cationic polymers such as protonated poly(vinylpyridine) (PVPH ) since the anion binds to multiple ion-exchange sites. 

Polymer metal complex formation of different polyvinylpyridines in solution, in hydrogels and at interfaces were investigated [83]. In aqueous solution linear or crosslinked polyvinylpyridines in the interaction with H2PtCl6 results in reduced viscosities and reduces swelling coefficients, respectively. Complexation leads to molecular bridges and folding of the polymer. Film formation was observed at the interface of poly(2-vinylpyridine) dissolved in benzene and metal salts dissolved in water. 

The use of static SIMS for the characterization of surfaces of polypropylene (PP), PTFE and a PMDA-ODA type poly-imide is described. Interfaces between evaporated copper or chromium films onto PTFE and polyimide were also analyzed. Some of the polymer substrates were modified by ion beams, corona discharge in air or plasma treatments in air, At and H2. It is demonstrated that SIMS is highly complementary to XPS for the analysis of such modified surfaces, in that effects such as crosslinking, unsaturation and formation of low-molecular weight material at surfaces can be detected. 

The formation of cylindrical domains of one block in a matrix of another, in diblock copolymers, has also been exploited for the generation of nanochannels in thin film membranes [40, 41]. Using diblock copolymers of PtBA-b-PCEMA, but this time with a larger volume fraction (ca. 74 vol%) of the photo-crosslinkable PCEMA block, Liu et al, prepared thin polymer films containing a densely packed array of nanocylinders (diameter 22 nm) [40]. As expected, in these cases the PCEMA block forms the continuous phase with nanocylinders of the hydrolyzable PtBA blocks forming a densely packed array. Typically, thick films (or disks of ca. 

Reactive plasticizers that polymerize after film formation, can also be used. They form an independent network (sometimes topologically resembling bailing wire) or crosslink the polymer. Thus, the reaction results in a nonvolatile IPN. The chemistry of the latex surface region can be arranged such that it can be plasticized with water. This may be satisfactory for situations where the surface chemistry will be altered later, or that water will not reach the final film in deleterious quantities. 

The efect of crosslinking on the dynamic mechanical properties of polymers has been studied for many years. But one should note a clear distinction in the case of film formation from disposions of crosslinked latex particles. Each particle is a microgel. The crosslinks are confined to the particle itself without any additional ctosslinking across the particle boundaries [68]. Of course in some systems, like those formed from butadiene-containing latexes or from other latexes containing reactive functional groups, cross-boundary crosslinking can occur subsequent to film formation. 

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