Ethylene oxide comonomers

THF copolymerizes readily with other cyclic ethers such as oxides and oxetanes. The comonomers used include ethylene oxide (67), propylene oxide (99,100), epichlorohydrin (ECH) (101,102), phenyl glycidyl ether (102), 3.3-bis(chloromethyl) oxetane (BCMO) (25, 98, 101, 103) and 3-methyl-3-chloromethyl oxetane (103). Just as in THF homo-polymerization, a large variety of catalysts have veen used. In many cases the kinetics of copolymerization have been studied. Table 22 summarizes the monomer reactivity ratios, rx (THF), and r2 (comonomer) which have... 

Polyformaldehyde. Polyformaldehyde or polyacetal is made by two different processes. Delrin is made from formaldehyde by anionic polymerization catalyzed by a tertiary amine. The homopolymer is end-capped with acetic anhydride. Celcon is made from trioxane cationic copolymerization using boron trifluoride catalyst and ethylene oxide (2-3%) as the comonomer. Boron trifluoride is a Lewis acid that associates with trioxane and opens up the six-membered ring. Ethylene oxide provides the end capping. Without an end cap, polyformaldehyde is thermally unstable and loses formaldehyde units. 

The copolymerisation of ethylene oxide and phenyl isocyanate has been found [266] to proceed in the presence of the triethylaluminium-water (2 1) catalyst, although phenyl isocyanate alone could not be polymerised by the same catalyst. The copolymer formed was characterised by an alternating comonomer distribution [scheme (39)] and contained acetalic units in its chains (Table 9.4) ... 

In food contact articles ethylene oxide, butane diolglyceride ether, butane diolfor-mal, 1,3-dioxane, 1,3-dioxolane (total < 6 %) can be used as comonomers. Amines, tri-phenylphosphine, borotrifluoride and others can be used as catalysts (total < 0.1 %) and various polymerization regulators and polymerization inhibitors can be used. 

In the copolymerization of trioxane with dioxolane, however, depolymerization and regeneration of dioxolane monomer is a faster and more effective way of converting soluble into crystalline copolymer with random distribution. A similar mechanism may hold true for trioxane polymerization with similar comonomers such as 1,3-dioxane, 1,3-dioxacyclo-heptane and in part even for copolymerization of trioxane with ethylene oxide which also involves formation of some dioxolane and soluble copolymer. 

It has to be remembered, however, that this process may be complemented by the reversibility of the propagation step. In the copolymerization of 1,3,5-trioxane with 1,3-dioxolane (or ethylene oxide), the complex set of equilibria is established, involving comonomers but also formalde-... 

The copolymerization between trioxane and suitable comonomers (ethylene oxide, 1,3-dioxolane, diethylene glycol formal, 1,4-butane diol formal in amounts of 2-5% by weight) is performed using cationic initiators. The cationic initiators could be Lewis acids, such as BF3 or its etherate BF3Bu20 which was used, for example by Celanese (the mechanism of this reaction was studied in detail [163,164]) or protic acids such as perchloric acid, perfluoroalkane sulfonic acids and their esters and anhydrides. Heteropoly acids were used and also a series of carbenium, oxocarbenium salts, onium compounds, and metal chelates. To regulate the molecular weight chain-transfer agents, such as methylal and butylal, are added. 

Usually, the copolymerization is carried out in bulk and the reaction is very rapid, completed in few minutes. Although the comonomer, e.g., ethylene oxide, is preferentially consumed at the beginning, the copolymer obtained has a statistical distribution of removal units, which is due to the occurring transacetalization reaction. 

The situation is still more complex, when like in commercial polymers of TXN, the solid phase contains two types of units (most frequently ethylene oxide units from ethylene oxide or 1,3-dioxolane comonomers). Comparison of comonomer contents in the crystalline region of as-polymerized and recrystallized samples shows that segregation occurs in recrystallized samples, leading to a higher fraction of comonomer in the amorphous than in the crystalline phase 78>. The density and melting points decrease with increasing content of the comonomer units in both as-polymerized and recrystallized samples as shown in Fig. 7.8. 

Polyoxymethylene polymers, POM, commonly known as polyacetals or Acetal resins are linear thermoplastic polymers containing predominantly the -CH -O- repeat unit in their backbone. There are two types of acetal resins available commercially (1) homopolymers made by the polymerization of formaldehyde, followed by endcapping, (2) copolymers derived from the ring opening polymerization of trioxane (a cyclic trimer of formaldehyde), and a small amount of a comonomer such as ethylene oxide. Acetal resins are... 

In contrast to acetal homopolymer, acetal copolymers have built-in heat stabilization. They are prepared by copolymerization of trioxane with small amounts of comonomer, usually cyclic ethers like ethylene oxide or 1,3-diozolane. 

For TOX copolymerization with ethylene oxide (EO), EO was first converted to low molecular weight copolymer and cyclic oligomers such as dioxolane (DOL) and 1,3,5-trioxepane (TOP) (4). For either EO and DOL as comonomer with TOX, they were found to be preferentially incorporated during the induction period (5). 

The commercial polymers are stabilized directly by additives in the polymerizing mixture, and this is in contrast to polymerization from formaldehyde, where the polymer is first produced and then subsequently stabilized. Here, a distinction is made between thermal degradation stabilization and stabilization against degradation induced by alkali. Cyclic ethers such as ethylene oxide are thermal stabilizers, that is, they stabilize against a depolymerization starting from the chain ends. They are quantitatively incorporated into the chain as comonomers at small yields ... 

The major commercial use of propylene oxide is as a comonomer for copolymerization. The block copolymerization with ethylene oxide produces water-soluble detergents. The copolymerization of propylene oxide with non-conjugated dienes produces sulfur-vulcanizable, oil-resistant elastomers that remain rubber-like at low temperatures. The elastomers obtained by the copolymerization of propylene oxide with allyl glycidyl ether have only poor oil resistance, but have good ozone resistance and remain rubberlike at low temperatures. 

Copolymer latices of styrene and acrylates (mainly butyl acrylate) were synthesised. Sodium dodecyl sulphate and ethoxylated nonyl phenol containing ten ethylene oxide units were used as surfactants and potassium persulphate as initiator. A coating for paper was made on the basis of the copolymer latices and white pigments. The performance of the coated paper was measured. By varying experimental conditions such as comonomer proportion and amounts of emulsifiers and of initiator, a copolymer latex suitable for paper coating was prepared. Paper coated with latex showed satisfactory properties in... 

Acetal homopolymers are polymerized from purified anhydrous formaldehyde. Acetal copolymers are copolymerized from cychc 1,3,5-tri-oxane cychc trimer (CsHeOa) of formaldehyde, tjrpically with a cychc ether comonomer such as ethylene oxide [1]. Ethylene glycol is the product of hydrolysis of ethylene oxide. 

The stereocopolymers of lactic acid, prepared by the polymerization of various stereoisomers, are discussed in a subsequent section in this book and will not be discussed here. Typical comonomers that have been used for lactic acid or lactide copolymerization are glycolic acid or glycolide (GA) [11-17], poly (ethylene glycol) (PEG) or poly(ethylene oxide) (PEG) [15 3], poly(propylene oxide) (PPO) [16-18], (7 )- 3-butyrolactone (BL), 6-valerolactone (VL) [44-46], E-caprolactone (CL) [47-54], 1,5-dioxepan-2-one (DXO) [55-60], trimethylene carbonate (TMC) [61],... 

The unique properties of PEG also referred to as PEG, such as solubility in water and polar organic solvents and its insolubility in nonpolar solvents such as ethyl ether and heptane, lack of toxicity, rapid clearance from the body [18], high mobility, and FDA approval for internal consumption, make it a suitable comonomer for the preparation of block copolymers of LA or LA-GA copolymers. The copolymerization of hydrophobic LLA with hydrophilic poly(ethylene oxide) or poly (propylene oxide) or their block copolymers has been used to prepare diblock or triblock copolymers [19-21]. Several triblock copolymers of LLA, D,L-lactide (DLLA), and PEG in which PEG forms the central block have been reported in the literature [22-27]. These copolymers are more hydrophilic, flexible, and biodegradable than PLLA homopolymer [28]. The hydrophilic domains of PEG act as a... 

Synthetic rubbers are produced as commodities. Polybutadiene, polybutylene, polychloroprene and polyepichlorohydrin are examples of elastomeric homopolymers. Copolymeric rubbers comprise poly-(butadiene-co-styrene), poly(butadiene-co-acryloni-trile), poly(ethylene-co-propylene-co-diene), and poly-(epichlorohydrin-co-ethylene oxide). The unsaturated group in the comonomer provides reactive sites for the crosslinking reactions. Copolymers combine resilience with resistance to chemical attack, or resilience in a larger temperature range, and thermoplastic-like properties. There are several studies in the literature describing the preparation of blends and composites of elastomers and conductive polymers. A description of some significant examples is given in this section. 

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