Polymer chemical bonding

In this chapter, we will be dealing with inorganic and/or coordination molecular materials. These materials are constructed from elementary bricks , and assembled, with or without the aid of another molecular element sometimes referred to as the mortar , to form an extended structure. In these superstructures, which may be designated inorganic or coordination polymers, chemical bonds and/or intermolecular interactions join the bricks to each other. The former may be covalent, ionic or hydrogen bonds, while the latter are most often n-n, electrostatic or van der Waals interactions. 

It is well known that thermoset polymers such as epoxy, vinyl ester, polyester, phenolic, etc., are chemically or physically cross-linked polymers (chemical bonds between polymer chains, intermolecular van der Waals bonds, dipole-dipole interactions, and molecular entanglement). These cross-links serve as molecular anchorages, which prevent molecular motion of the... 

In the case of ion exchangers, the primary ions are chemically bonded into the ftamework of the polymer, and the exchange is between ions in the secondary layer. A few illustrations of these various types of processes follow. 

One potential approach extends the idea of chemical amplification introduced in our preceding description of dry-film resists. In 1982, Ito and co-workers (37,38) recognized that if a photosensitizer producing an acidic product is photolyzed in a polymer matrix containing acid-labile groups, the acid will serve as a spatially localized catalyst for the formation or cleavage of chemical bonds. 

Antioxidants. The 1,2-dihydroquinolines have been used in a variety of ways as antioxidants (qv). For example, l,2-dihydro-2,2,4-trimethylquinoline along with its 6-decyl [81045-48-9] and 6-ethoxy [91-53-2] derivatives have been used as antio2onants (qv) and stabilizers (68). A polymer [26780-96-1] of l,2-dihydro-2,2,4-trimethylquinoline is used in resins, copolymers, lubricant oils, and synthetic fibers (69). These same compounds react with aldehydes and the products are useful as food antioxidants (70). A cross-linked polyethylene prepared with peroxides and other monomers in the presence of l,2-dihydro-6-ethoxyquinoline produces polymers with a chemically bonded antioxidant (71). 

Many metal ions react with water to produce hydrolysis products that are multiply charged inorganic polymers. These may react specifically with negative sites on the colloidal particles to form relatively strong chemical bonds, or they may be adsorbed at the interface. In either case, the charge on the particle is reduced. 

A polymer blend is a physical or mechanical blend (alloy) of two or more homopolymers or copolymers. Although a polymer blend is not a copolymer according to the above definition, it is mentioned here because of its commercial importance and the frequency with which blends are compared with chemically bonded copolymers. Another technologically significant material relative to the copolymer is the composite, a physical or mechanical combination of a polymer with some unlike material, eg, reinforcing materials such as carbon black, graphite fiber, and glass (see Composite materials). 

In the pendent chain systems, the dmg is chemically bound to a polymer backbone and is released by hydrolytic or enzymatic cleavage of the chemical bond. The dmg may be attached directiy to the polymer or may be linked via a spacer group. The spacer group may be used to affect the rate of dmg release and the hydrophilicity of the system. These systems allow very high dmg loadings (over 80 wt %) (89) which decrease the cost of the polymeric materials used ia the systems. These systems have beea examiaed by many iavestigators (111,112). 

As mentioned earlier, adhesive bond formation is governed by interfacial processes occurring between the adhering surfaces. These interfacial processes, as summarized by Brown [13] include (1) van der Waals or other non-covalent interactions that form bonds across the interface (2) interdiffusion of polymer chains across the interface and coupling of the interfacial chains with the bulk polymer and (3) formation of primary chemical bonds between chains or molecules at or across the interface. 

On the organic side of the interface, chemical bonds are formed between the organofunctional R group of the silane and the reactive species in the polymer matrix. For example, a methacrylate- or styryl-functional silane reacts with polyesters copolymerized with styrene or similar monomers, while amino- or chloroalkyl-functional silanes are unsuitable in this particular case. Polybutadiene... 

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