Oligomers polyfunctional

Traditionally, we create thermoset polymers during step growth polymerization by adding sufficient levels of a polyfunctional monomer to the reaction mixture so that an interconnected network can form. An example of a network formed from trifimctional monomers is shown in Fig. 2.12b). Each of the functional groups can react with compatible functional groups on monomers, dimers, trimers, oligomers, and polymers to create a three-dimensional network of polymer chains. 

The curing reaction of acrylates is typical of vinyl monomers. Therefore, the degree of double-bond conversion is the measure of the degree of cure. The best results are obtained when using oligomers as binders and monomers as reactive thinners. Examples of difunctional and polyfunctional acrylates are in Table 4.4. A partial list of the most common acrylate oligomers is below. - ... 

All BMI building blocks and maleimide-terminated oligomers discussed previously are synthesized from the corresponding polyamine precursor and maleic anhydride simply because of economic reasons. However, there are other synthetic methods available, for instance, the reaction of a functionalized monomaleimide with a polyfunctional monomer or oligomer. Such a functionalized monomaleimide is maleimido benzoic acid or its acid halide. These were used to synthesize maleimide-terminated polyamides (39, 40) or polyesters (41), respectively. 

The chemistry involved in both systems involves the photo-initiated, free-radical polymerization of polyfunctional ethylenically unsaturated oligomers and monomers. 

As is well known, two main routes can be adopted for obtaining crosslinked derivatives, as schematically depicted in Fig. 159 these include u.se of polyfunctional oligomers or monomers (route a) and reaction of high-molecular-weight linear polymers with crosslinking reagents (route b). 

Dienes. The dienes present a particularly challenging case since both stereoisomerism and geometric isomerism can be observed in the products (the dienes are not only polyfunctional but also permit different tacticities). For butadiene, the following possibilities exist trans-1,4 cis-1,4 atactic 1,2 isotactic 1,2 syndiotactic 1,2 cyclic oligomers and cyclic high polymers (Reaction 16). 

Hydrosilylation of unsaturated organosilicon compounds has also found several applications in molecular and polymer organosilicon chemistry. In particular, the addition of polyfunctional silicon hydrides to poly(vinyl)organosiloxane, catalyzed exclusively by Pt compounds and providing an activated cure for silicon rubber [10], has been of great practical importance. Hydrosilylation of the vinyl group at silicon seems to be effective synthetic method for preparation of oligomers and polymers with a linear or cyclolinear stmcture (polyhydrosilylation), and can occur either via the addition of dihydro-carbosilanes and -siloxanes to divinyl-silanes and -siloxanes [25, 26] or by intermolecular hydrosilylation [4] (eq. (1)). 

Silyl anions, electrogenerated by the cathodic reduction of polyfunctional chlorosilanes, react with remaining Si—Cl bonds of the starting molecules or of intermediately formed oligomers to give linear polysilanes. The molecular mass of the resulting polysilanes depends on the electrolysis conditions (solvent, electrode material, supporting salt, etc.) [102,... 

The uncured conformal coatings are clear, transparent liquids with viscosities of 700 to 1400 cp at 25°C. A typical composition which has a viscosity of 820 cp at 25°C consists of 43 wt % of a high viscosity urethane acrylate oligomer, 49 wt % of a low viscosity monoacrylate diluent, 5 wt % of a polyfunctional thiol, 2 wt % of benzopinacol and 1 wt % of alpha, alpha-dimethoxy-alpha-phenylacetophenone. A trace amount of a fluorescent dye may be added, if desired, to facilitate inspection of the finished coating. 

The most common acrylic polymer is polymethyl methacrylate, which is obtained by polymerization of methyl methacrylate (MMA). The material consists of a highway-grade aggregate and a matrix produced by cross-linking MMA with trimethylol propane trimethacrylate or other polyfunctional acrylic oligomers. 

At the same time there is the scarcity of commercially available polyfunctional cyclic carbonates (Structure 4.2). There are several methods for producing polymers or oligomers containing multiple cyclic carbonate groups ... 

Figovsky, O., Shapovalov, L., Blank, N., and Buslov, F. Method of Synthesis of Polyfunctional Hydroxyurethane Oligomers and Hybrid Polymers Formed Therefrom . EP Patent 1070733, Issued January 24, 2001. 

Chain Extenders and Cross-linkers. In addition to the two principal components of most urethane coatings, isocyanate and polyol components, a number of di- or polyfunctional, active hydrogen components may be used as chain extenders or cross-linkers. The most important classes of compounds for this use are diols or polyols (monomers or oligomers), diamines, and alkanolamines. Typical examples of diols are ethylene, dlethylene, dlpropylene glycol, 1,4-butanedio1, 1,5-hexanediol, neopentyl glycol,... 

Crude EA oligomer is used which contains polyfunctional hydrophobe-ethoxylate units. 

Polyurethanes are thermoset polymers formed from di-isocyanates and polyfunctional compounds containing numerous hydroxy-groups. Typically the starting materials are themselves polymeric, but comprise relatively few monomer units in the molecule. Low relative molar mass species of this kind are known generally as oligomers. Typical oligomers for the preparation of polyurethanes are polyesters and polyethers. These are usually prepared to include a small proportion of monomeric trifunctional hydroxy compounds, such as trimethylolpropane, in the backbone, so that they contain pendant hydroxyls which act as the sites of crosslinking. A number of different di-isocyanates are used commercially typical examples are shown in Table 1.2. 

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