Straight-chain polymer

The simplest case of structure-property relationships are qualitative rules of thumb. For example, the statement that branched polymers are generally more biodegradable than straight-chain polymers is a qualitative structure-property relationship. 

An area of great interest in the polymer chemistry field is structure-activity relationships. In the simplest form, these can be qualitative descriptions, such as the observation that branched polymers are more biodegradable than straight-chain polymers. Computational simulations are more often directed toward the quantitative prediction of properties, such as the tensile strength of the bulk material. 

Oils and gums are nonhighly branched- or straight-chain polymers whose viscosity increases with the degree of polycondensation. 

In a 5 liter three-necked flask, fitted with a reflux condenser, agitator and thermometer, were placed 1,393 g (9.41 mols) of redistilled (CH3)2Si(OEt)2 and 1,1 lOg (9.41 mols) of (CH3)3SiOEt. To this solution was added 254 g (14.11 mols) of water containing 7.5 g of NaOH (approximately 1 NaOH per 100 silicon atoms). This insured the formation of only straight chain polymers. The mixture was heated to 40°C and the temperature continued to rise for nearly an hour. After adding 50 cc (20% excess) more water, the mixture was refluxed for two hours and then allowed to stand overnight. 

PMA is usually available as a 50% actives material. It is a straight-chain polymer and has a molecular weight of approx. 1000. Dose rate again depends on the application but is usually low, say 1.0 to 2.5 ppm actives. 

Cellulose Cellulose is a straight-chain polymer of glucose units linked by (31-4 bonds. The polysaccharide chains are aligned to form fibrils that have great tensile strength. Cellulases, enzymes that degrade cellulose, are absent in mammals but are produced by some bacteria, fungi and protozoa. 

FIGURE 15.4 Degradation of ladder polymer and straight-chain polymer due to thermal aging. 

When cyclic alkenes are utilized as starting materials the metathesis reaction will lead to long chain polymers and/or cyclic oligomers [103, 104, 107, 108]. If a strained cyclic alkene is employed the reaction is effectively irreversible. Industrially cyclooctene (polymer Vestenamer), 2-norbornene (polymer Norsorex), and dicyclopentadiene (polymer Telene, Metton, Pentam) are used as monomers. Upon polymerization cyclooctene and 2-norbornene yield straight chain polymers while dicyclopentadiene also allows cross-linking (Scheme 5.56). 

One important example of cross-linking involves phenol-formaldehyde copolymers (Fig. 23.3). When these two compounds are mixed (with the phenol in excess in the presence of an acid catalyst), straight-chain polymers form. The first step is the addition of formaldehyde to phenol to give methylolphenol ... 

This plastic is a partially fluorinated straight-chain polymer with a very high molecular weight. It is produced by free-radical polymerization mechanism in a solvent or a hybrid (a solvent/aqueous mixture) media, using an organic peroxide initiator. Copolymerization of tetrafluoroethylene and ethylene (CH2=CH2, molecular weight 28, CAS number 74-85-1) proceeds by an addition mechanism. 

Since an active OH group is left at each end of chain, polymerisation reaction continues and the length of the chain continue to increase. The starting materials for the manufacture of silicones are alkyl or aryl substituted chlorosilanes. Methyl compounds are mainly used, though some phenyl derivatives are used as well. Hydrolysis of dimethyldichlorosilane (CH3)2SiCl2 gives rise to straight chain polymers and, as an... 

The interaction between dimethyldiethoxy silane and trimethylethoxy silane with water, in the presence of 1 NaOH per 100 silicon atoms, gives rise to the formation of simethicone with the elimination of a calculated amount of ethanol. The presence of NaOH, as a catalyst, ensures the formation of only straight chain polymers. 

Starch, a polymer of a-D-glucose, consists of two parts amylose, a straight-chain polymer of a-glucose [see Fig. 21.33(a)], and amylopectin, a... 

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