Polymer linkage

Fig. 5. Chemistry of cyclized mbbei—bis-a2ide negative acting resist, (a) Preparation of cyclized mbber resin from polyisoprene (b) photochemistry of aromatic bis-a2ide sensiti2ers. The primary photoproduct is a highly reactive nitrene which may combine with molecular oxygen to form oxygenated products, or may react with the resin matrix by addition or insertion to form polymer—polymer linkages.

The configuration of each anomeric hydroxyl group that forms a polymer linkage is fixed, and the type of linkage has a significant effect on the physical properties of the polymer, as will be seen. 

Chenera B, Finkelstein JA, Veber DF. Protodetachable arylsilane polymer linkages for use in solid phase organic synthesis. J Am Chem Soc 1995 117 11999-12000. 

The chemical nature of the main-chain linkages of step-growth polymers makes this class of polymers particularly reactive to a wide variety of chemical species. Solvolysis reactions break the C-X bond at the polymer linkage bonds. These types of reactions are often pH-dependent, so the stability of the polymer is highly dependent on the acidity or basicity of the prodegradant. 

Polymer linkages that do not release condensates on being formed include polyurethanes (diisocyanate/polyalcohol) and epoxy (ring opening of the epoxy... 

Polymer Linkage-Type and Alignment of Amino Acid Sequences of Various (Mutant) Glucansucrase Enzymes with GTFR Wild-Type and Mutant Variants58... 

More importantly, understanding the chemistry of PP requires you to know the critical difference between PP and the polyethylenes—the asymmetry of the PP molecules. backbone. In polyethylene, every carbon looks like every other carbon in the chain. In PP, the polymer linkage is between succeeding double-bonded carbons, like polyethylene. But, the methyl group survives as a branch on every second carbon in the PP backbone chain. See Figure 23—7.) Furthermore, the orientation of that branch is crucial to the properties of the polymer. See Figure 23-8.)... 

Figure 16. Crosslinking reactions in bisarylazide-rubber resists. The primary photoevent is production of a nitrene which then undergoes a variety of reactions that result in covalent, polymer-polymer linkages. A schematic representation of crosslinking via nitrene insertion to form aziridine linkages is shown together with several other reaction modes available to the...

Chenera, B. Finkelstein, J. A. Veber, D. F. Protodetachable Arylsilane Polymer Linkages for Use in Solid Phase Organic Synthesis, J. Am. Chem. Soc. 1995,117, 11999-12000. 

Supramolecular chemistry allows novel kinds of polymer linkages such as the mechanical links found in polycatenanes and polyrotaxanes. 

Unlike Lys-PEG, the polymer linkage at His34 has a reversible nature, which yields to a pro-drug-like derivative [26]. 

Various studies indicate that certain alkoxysilanes react with surface silanol groups (2, 8), but nothing appears to have been reported for ETES and VTES specifically. The second type reaction is between two adsorbate molecules to form a siloxane polymer linkage. 

Table 1 Polymer linkage type and alignment of amino acid sequences of various (mutant) glucansucrase enzymes with GTFR wild-type and mutant variants derived [52]...

More specifically, the acyclic alkenes is defined gation, condensation-type polymerization, where the term condensation-type arises from the liberation of a by-product that advances the reaction. The other possibility for step polymerization is addition-type, where the resulting polymer linkage is an adduct of the two monomers, and no atoms are lost (e g. polyurethanes). 

Gais, H.J., Rupert, S., Modification and immobilization of proteins with polyethylene glycol tresylates and polysaccharide tresylates evidence suggesting a revision of the coupling mechanism and structure of the polymer-polymer linkage. Tetrahedron Lett. 36, 3837-3838, 1995. 

The fact that the decrease in molecular weight in the photodegradation of polymethylvinylketone does not continue at the same rate throughout the irradiation has been ascribed to the occurrence of a competing reaction that opposes the main chain scission process. This is assumed to be the formation of new polymer—polymer linkages by mutual recombination of macro-radicals resulting from the addition of CHj or CH3—CO to unsaturated chain ends formed in the Norrish type II reaction [55]. Evidence for the presence of such macro-radicals is found in the production of graft copolymers when solutions of polymethylvinylketone in various monomers (acrylonitrile, methyl methacrylate, vinyl acetate) are irradiated [57]. 

Step-growth Polymerization The simplest scheme of this polymerization involves the reaction of a difunctional monomer AB, which contains both functional groups A and B in the molecule. For example, A can be an amine and B a carboxylic acid group. Another scheme involves the reaction between two difunctional monomers of the type AA and BB. In any case, each polymer linkage will have involved the reaction of the functional groups A and B coming from two molecules (monomers or chains). Some examples of polymers synthesized by this mechanism are polyurethane, polyamide, and polyester. 

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