Glycolic acid, copolymerization with

The best separations of polyols have been achieved on mixed phase packings, which combine the high resolving capacity of the polar phase with the stability of the nonpolar phase. Reported stationary phases are 2-10% EGSS-X (ethylene glycol succinate copolymerized with dimethyl polysiloxane) or ECNSS-M (ethylene glycol succinate copolymerized with cyano-ethyl methyl polysiloxane) on uncoated adsorbent from diatomite, acid washed, and dimethylchlorosi-lane-treated or uncoated adsorbent from diatomite acid-washed and silanized, 3% XE-60 (poly(methyl cyanopropyl siloxane)) on uncoated adsorbent from diatomite acid-washed and silanized, GP 3% SP-2340 (poly(dicyanopropyl siloxane)) on diatomite support and many other combinations. 

Glycerol can be selectively dehydroxylated to either 1,2-propanediol (1,2-PDO), a chemical that can advantageously replace ethylene glycol as anti-freezing agent, or 1,3-propanediol (1,3-PDO), which when copolymerized with terephthalic acid... 

The sole use for para-xylene is to make terephthalic acid (TPA) and its derivative, dimethyl terephthalate (DMT). When DMT is copolymerized with ethylene glycol, chemists call it polyethylene terephthalate. On Seventh Avenue in New York, they call it polyester. On the labels, it is sometimes called Dacron. 

The dimethyl ester of this acid in solution shows a quantum efficiency photochemical products. On the other hand, when the same acid is copolymerized with a glycol to form a polymeric compound with molecular weight 10,000 the quantum yield drops by about two orders of magnitude, 0.012. The reason for this behavior appears to be that when the chromophore is in the backbone of a long polymer chain the mobility of the two fragments formed in the photochemical process is severely restricted and as a result the photochemical reactions are much reduced. If radicals are formed the chances are very good that they will recombine within the solvent cage before they can escape and form further products. Presumably the Norrish type II process also is restricted by a mechanism which will be discussed below. 

Thermoplastic poly(lactic acid) (PLA) is obtained by polycondensation of the acid or by ring-opening of the lactide. Its mechanical performance is similar to that of PS. Lactic acid (LA) can be produced by fermentation of coal, petroleum or namral gas. PLA is sensitive to enzymatic and chemical hydrolysis. It has been used for medical implants, dmg delivery, packaging and consumer goods. LA can be copolymerized with ethylene glycol into highly hydrophilic poly(ether-ester) block copolymers. Similarly, LA was copolymerized... 

Polymer plasticization can be achieved either through internal or external incorporation of the plasticizer into the polymer. Internal plasticization involves copolymerization of the monomers of the desired polymer and that of the plasticizer so that the plasticizer is an integral part of the polymer chain. In this case, the plasticizer is usually a polymer with a low Tg. The most widely used internal plasticizer monomers are vinyl acetate and vinylidene chloride. External plasticizers are those incorporated into the resin as an external additive. Typical low-molecular-weight external plasticizers for PVC are esters formed from the reaction of acids or acid anhydrides with alcohols. The acids include ortho- and iso-or terephthalic, benzoic, and trimellitic acids, which are cyclic or adipic, azeleic, sebacic, and phosphoric acids, which are linear. The alcohol may be monohydric such as 2-ethylhexanol, butanol, or isononyl alcohol or polyhydric such as ethylene or propylene glycol. The structures of some plasticizers of PVC are shown in Table 9.1. 

Unsaturated network polyesters may be produced by using an unsaturated dibasic acid or glycol or both. Typically the unsaturated dibasic acid, such as maleic anhydride or fumaric acid, is copolymerized with a saturated acid such as phthalic acid and a glycol (e.g., propylene glycol or diethylene glycol). 

Mention may also be made here of the 2-hydroxyethyl ester of methacrylic acid, which is the monomer used for soft contact lenses. Copolymerization with ethylene glycol dimethacrylate produces a hydrophilic network polymer (a hydrogel). Hydrogel polymers are brittle and glassy when dry but become soft and plastic on swelling in water. 

Fukuzaki, H., Yoshida, M., Asano, M., Aiba, Y., and Kumakura, M., 1989. Direct copolymerization of glycolic acid with lactones in the absence of catalysts. Eur. Polym. J., 26 457-461. 

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