Crosslinking in situ

Keywords compatibilization, functionalization, reactive processing, blends, copolymer crosslinking, in-situ formed copolymers, low molecular weight compatibilizers, miscibility. 

ProliforOUS Polymerization. Early attempts to polymerize VP anioni-cally resulted in proliferous or popcorn polymerization (47). This was foimd to be a special form of free-radical addition polymerization, and not an example of anionic polymerization, as originally thought. VP contains a relatively acidic proton alpha to the pyrrolidinone carbonyl. In the presence of strong base such as sodium hydroxide, VP forms crosslinkers in situ, probably by the following mechanism ... 

Approaches that use specially synthesized reactive compatibilizers and that can account for the formation of compatibilizing crosslinks in situ are mostly too expensive for commingled post-consumer waste recyclates. 

Polymers also are used to improve volumetric sweep efficiency in reservoirs that are fractured or have considerable permeability variation. In this application, commonly called in-situ permeability modification, the polymer is crosslinked in situ to form a gel network. In-situ gelation reduces the permeability in the region contacted by the polymer. By selection of chemical systems, treatments... 

In a departure from historical approaches to introducing fillers in UHMWPE, researchers from Colorado State University have developed a novel UHMWPE-hyaluronan microcomposite [50, 51]. This microcomposite is detailed in Chapter 18. Hyaluronan is a natural lubricant in articular cartilage. By incorporating this biomolecule into UHMWPE, researchers theorized that wear could be reduced. Because hyaluronan is hydrophilic and UHMWPE is hydrophobic, fabrication of an UHMWPE-hyaluronan microcomposite is by no means a straightforward proposition and is accomplished via a complex and elegant multistep procedure. The process, which is described in greater detail in Chapter 18, begins with the production of a porous UHMWPE substrate, which constitutes the matrix of the microcomposite. The hyaluronan is complexed with quaternary ammonium cations (CTA-I-) and silylated [52]. A solution of silyl hyaluronan-CTA is then diffused into the open celled porous UHMWPE matrix, chemically crosslinked in situ, and then hydrolyzed... 

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