Polymers vinyl-type monomer

A number of reports in the literature describe the use of alkyl thiosulfates to modify reactive vinyl type monomers and/or preformed polymers with the expressed goals of producing polymers with enhanced water solubility (1-61. The alkylthiosulfate modified polymers have been shown to be thermally and photochemically reactive and capable of producing crosslinked films with varying degrees of stability (5). 

The initiation of polymerization by ultraviolet radiation has been of particular interest in the study of free radical processes [1,2]. The test tube demonstration described here is simple and may be used to evaluate the polymerizabil-ity of new monomers or to study some of the physical properties of a polymer. Although the method is particularly effective for acrylic and methacrylic monomers, it may also be applied to the polymerization of a wide range of vinyl -type monomers. 

During the early 1960 s a new class of chemicals containing one or more double bonds was used to treat wood vinyl type monomers that could be polymerized into the solid polymer by means of free radicals (2). This vinyl polymerization was an improvement over the condensation polymerization reaction because the free radical catalyst was neither acidic nor basic, nor does the reaction leave behind a reaction product that must be removed from the final composite, such as water. The acid and base catalysts used with the other treatments degrade the cellulose chain and cause brittleness of the composite. Vinyl polymers have a large range of properties from soft rubber to hard brittle solids depending upon the groups attached to the carbon-carbon backbone. 

Some of the most important linear or chain polymers belong to the category of homopolymers, for example, polyethylene, polyvinylchloride, and polypropylene (see Table 2.1) where the vinyl-type monomer (see Figure 2.34) with different side groups, R, is repeated [8,195],... 

There are, in general, two ways to prepare new polymers which have valuable and "useful properties. One of them involves the synthesis of a new monomer, which embodies by virtue of its chemical nature some interesting and attractive features. If one then polymerizes such a monomer, one finds in the polymer the desired properties resulting from repetition of a large number of monomeric units. In this manner, many new addition polymers have been made from vinyl-type monomers, which had reactive groups such as —CH—CH2, —SH, or —NHCH2OH. The... 

Treatment of solid wood over the years for increased utility included many chemical systems that affected the cell wall and filled the void spaces in the wood. Some of these treatments found commercial applications, while some remain laboratory curiosities. A brief description of the earlier treatments is given for heat-stabilized wood, phenol-formaldehyde-treated veneers, bulking of the cell wall with polyethylene glycol, ozone gas-phase treatment, ammonia liquid- and gas-phase treatment, and p- and y-radiation. Many of these treatments led to commercial products, such as Staybwood, Staypak, Im-preg, and Compreg. This chapter is concerned primarily with wood-polymer composites using vinyl monomers. Generally, wood-polymers imply bulk polymerization of a vinyl-type monomer in the void spaces of solid wood. 

Most vinyl type monomers form during polymerization Fl-T type polymers. However, a certain proportion of H-H polymer may be formed during radicalic polymerization. An example of differentiation between H-T and H-H polymer using pyrolysis data was reported for polystyrene [3]. Although during pyrolysis the yield of monomer is not different between H-T and H-H polymers, other small molecules may indicate the structural differences, as shown in the schemes below that indicate the main compounds formed in the thermal decomposition process for the H-T polymer ... 

Metal complexes bound to a polymer support most frequently induce ionic polymerization of olefins, dienes and acetylenes, and less commonly radical polymerization of vinyl-type monomers, acting at all reaction stages initiation, chain propagation and termination. Active sites for the addition of monomer molecules to the growing polymer chain can in many cases be regenerated yielding new polymer chains (catalysis via a polymer chain). 

Complexes of Cu(II), Fe(III), V(V), etc., immobilized on polymers, are often used as components of redox systems which are effective as initiators of vinyl-type monomer polymerization. For instance, the system vanadylpolycarboxylate-thio-... 

Uses As comonomer with vinyl-type monomers to produce crosslinked polymers reactive diluent in radiation-cured coatings Manuf./Distrib. ABCR UK http //www.abcr.de, Aldrich http //www.sigma-aldrich.com, Alfa Aesar http //www.aifa.com, Monomer-Polymer Dajac Labs Narchem http //www. narchem. com Allyl alcohol... 

Unsaturated polyester resins are complex polymers resulting from a crosslinking reaction of a liquid unsaturated polyester with vinyl-type monomers, most often a styrene monomer. The unsaturated polyester is formed via the condensation reaction of an unsaturated dibasic acid or anhydride, a saturated dibasic acid or anhydride, and a polyfunctional alcohol [32]. 

As has been noted previously, the cross-linking of unsaturated linear polyesters involves the reaction of the unsaturated sites in the polymer chain with a vinyl-type monomer. This reaction is analogous to conventional vinyl copolymerization and proceeds by an essentially similar mechanism. As carried out in commercial practice, cross-linking of unsaturated polyesters is invariably a free radical reaction. Two types of initiating systems are commonly employed for this reaction, namely those effective at elevated temperatures and those effective at room temperature. 

These elastomers have saturated main polymer chains and are usually prepared from ethylene or vinyl type monomers containing one double band. 

Chain Polymerization n Polymerization processes are of two basic types stepwise (or step reaction) and chain reaction. The kinetics of the two types of reaction are entirely different the properties of the polymers they produce differ with respect to molecular weight distribution and usually, although not inevitably, differ in kind. The vast majority of chain reaction polymerize-tions are those generally known as addition polymerizations involving the conversion of vinyl-type monomers. 

It is well known that oxygen inhibits the homopolymerization of vinyl-type monomers. Poly(maleic anhydride) is also best obtained when oxygen is excluded from polymerization solutions of MA and peroxide initiators. Substantially colorless polymer is obtained when both oxygen and UV light are excluded. 

These competitive equilibria, ion pair interchange rates and stereochemical propagation rates are not only affected by temperature but also by monomer structure, solvent, and counterion. Hence anionic and cationic polymerization reactions are much more complicated, but also much more versatile, than free radical reations. Data for polymer tacticities obtained in anionic and cationic polymerization reactions of vinyl-type monomers as a function of polymerization conditions are collected in Tables 5 and 6, respectivley (3). 

In simple homopolymerization of vinyl type monomers with optically active centers in the side chain, an optically active polymer resulted, which always lost all its optical properties as the side chain center was removed. The main experimental difficulty is that the complete removal is not always easily verified. This observation is valid both for polymers obtained by radical processes using optically active initiators or with an asymmetric physical agent like circularly polarized light. 

The first reported vinyl-type monomers of 5-fluorouracil appear to be the carbamoyl derivatives which were made as shown in Equation (1). The vinylcarbamoyl derivative (Ila) has been obtained in 42% yield and readily polymerizes under radical initiation. The pol3nner is active against P388 leukemia but it is not certain whether this is due to activity of the polymer or to a slow release of 5-FU by this polymer in an aqueous system (41-43). The isopropenylcarbamoyl derivative (Ilb) also polymerized under radical conditions but not as well as the vinylcarbamoyl derivative. The allylcarbamoyl derivative (lie) does not appear to polymerize or copolymerize (41). 

Recently Butler, et al have prepared another vinyl-type monomer containing 5-fluorouracil by the reaction of 5-FU with methyl fumaroyl chloride and this is shown below as (V). This monomer hydrolyzes rapidly in water but many of the copolymers hydrolyze more slowly and these polymers show promise as an anti-tumor system (47). Controlled release of 5-FU from various polymeric matrices has also been reported recently (48). 

With the exception of LDPE, polyolefins like other polyethylenes and polypropylene, which represent the largest amount of vinyl-type polymers produced in the world, are neither synthesized by radical nor by classical ionic polymerisation processes. Different types of polymerisation catalysts are in use for these purposes. The Cr-based Phillips catalyst, Ziegler-Natta type catalysts, metallocene or other more recently discovered catalysts, including late transition metal catalysts, are all characterized by their propagation step where the olefin monomer inserts into a carbon-transition metal link. ... 

The degree of cross-linking has been expressed by many different quantities. For vinyl-type polymers, where there arc two backbone atoms per monomer unit. 

Alkenyloxystyrene monomers such as 4-allyloxystyrene are useful components of photocured cationically polymerizable compositions. Used alone or in combination with divinyl ethers they provide low viscosity formulations, which are excellent solvents for commercial onium salt photoinitiators. Photocuring rates are comparable to vinyl ether monomers and the initially photocured alkenyloxystyrene polymers may be further heat processed to yield crosslinked phenolic type resins having outstanding thermal resistance properties. The new materials have good adhesive properties and are potentially useful where a combination of ease of processability and high performance is required. 

Hyperbranched polymers can be synthesized in several different ways, the most commonly used being classical condensation reactions. These reactions are made either in bulk or in solution where the A,jB monomers are condensed by themselves or in combination with a By core monomer. The use of a By core monomer improves the control over the molecular weight and dispersity of the hyperbranched polymer. Hyperbranched polymers can also be synthesized by self-condensing vinyl polymerization using vinyl-functional monomers. The introduction of this approach has greatly increased the number of possible monomers that can be used for this type of polymer. 

Suspension polymerization. In this process, monomers and initiator are suspended as droplets in water or a similar medium. The droplets are maintained in suspension by agitation (active mixing). Sometimes a water-soluble polymer like methylcellulose or a finely divided clay is added to help stabilize or maintain the droplets. After formation, the polymer, is separated and dried. This route is used commercially for vinyl-type polymers such as polyvinyl chloride and polystyrene. 

In particular, EVA waxes refer generally to oligomeric polymer compounds. They are prepared by the copolymerization of ethylene monomers and vinyl acetate monomers in the same way as the high molecular weight types. 

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