Chain copolymerization graft

Bulk polymerizations, such as addition (free-radical- and ionic-based) and step-growth types. Grafting polymerization by small molecules. Interchain copolymer formation, based on chain cleavage, graft copolymerization, and end-group block copolymerization. 

On further examination, over half of the AST patents listed were classified as associative in this review. Although most of these occur in more recent years, the earliest found (59) happens to be the first entry in the tables. In this and four other former issues (62, 64, 69, 70) that differ in the type of hydrophobic monomer employed, a maleic-anhydride-con-taining prepolymer is prepared and subsequently post-esterified with a nonionic surfactant. In essence, the associative side chains are grafted onto the polymer backbone. In nearly all of the other associative patents, the associative monomers are synthesized first and then copolymerized with the carboxylic acid and hydrophobic monomers. Many similarities also exist between the various associative AST patents. In refs. 62, 64, 69, and 70, the hydrophobic monomer was an obvious variable. In some others, differentiation is a manifestation of the type of coupling agent used. 

Differential thermal analysis (DTG) deals with the rate of decomposition of mass with respect to time. In the case of most of the graft copolymers, rate of weight loss as a function of time (mg/min) is lower than that of backbones [68]. However, in some other cases it has been found to be higher due to the disturbance in the crystalline lattice of the natural polysaccharides upon the incorporation of polyvinyl chains through graft copolymerization (Figure 2.7). 

Graft-Polyols Polyurethane foams are synthesized from the polycondensation reaction between a polyol and a diisocyanate. Polyols can be of two types conventional ones (polyethers) and graft-polyols [50]. The latter are obtained by the copolymerization of SAN in the presence of a polyol polyether using a free-radical initiator. Some of the SAN chains are grafted to the polyol backbone, while others remain free. The grafting is promoted... 

Copolymerizations are powerful ways to produce polymers with speeifie properties with well defined strueture. However, they involve the costly modification of existing production facilities of polystyrenes. To satisfy small market niches, modified polystyrenes ean be obtained through grafting reactions by chemical reactions on a polymer melt in an extruder (reactive extrusion) to achieve functionalities on the polymeric chains. Thus, grafting reactions are the preferred methods to achieve functionality commercially because they are low cost alternatives to the eopolymerization processes despite low grafting efficieney. For example, polystyrenes have been grafted with brominated styrene to enhanee the flame resistance of polystyrenes, as shown in Reaction 13. 

Similarly, Liu et prepared graft copolymers comprising poly(acrylic add) (PAA) backbone and side-chain PNIPAAm grafts that exhibited pH-responsive (due to PAA) and thermo-responsive (due to PNIPAAm) behavior. The macromolecules were formed by AIBN-initiated direct copolymerization in solution. No effert of comonomer sequences on the phase behavior was reported, although the system would, in prindple, allow for probing this effect efficiently. 

Graft copolymerization Graft copolymers are a type of branched copolymers with distinct side structures from the main chain. Graft copolymerization initiates the free radicals on cellulose molecule that can react with the hydrogen bonds on the matrix. Acrylic acid, acrylonitrile, and vinyl monomers are used for graft copolymerization of natural fibers. Equation 9.3 depicts the reaction of acrylonitrile with the fiber... 

Graft copolymers are produced by chain copolymerization of the macromonomer with another ethylenic monomer. This enables more well-defined graft copolymers to be prepared, especially with regard to the molar mass and molar mass distribution of the branches since these properties are defined by those of the macromonomer. 

The backbone chain is made by free radical copolymerization of styrene with some acryloyl chloride. It is reacted in THF solution with silver hexafluoroantimonate. The oxocarbenium salt formed immediately initiates the polymerization of THF (Scheme 23). However, the growth of the grafts has to be stopped at an early stage (by induced deactivation) to prevent formation of bridges between individual chains. The graft copolymers obtained have been characterized accurately. 

Many graft copolymers have been made by free radical copolymerization of co-styryl or co-methacryloyloxy macromonomers and various comonomers. Special interest has been devoted to amphiphilic copolymers involving a hydrophilic backbone and hydrophobic grafts, or vice versaf Poly(perfluoroalkyl methacrylate) and poly(stearyl methacrylate) are typical examples of hydrophobic polymers, whereas poly(hydroxyethyl methacrylate) or poly(vinylpyrrolidone) are examples of nonionic hydrophilic chains. Such graft copolymers have found a number of applications as surface modifiers or coatings because of their ability to give intramolecular phase separation (surface accumulation phenomena ). 

Uses. Vinyhdene fluoride is used for the manufacture of PVDF and for copolymerization with many fluorinated monomers. One commercially significant use is the manufacture of high performance fluoroelastomers that include copolymers of VDF with hexafluoropropylene (HFP) (62) or chlorotrifluoroethylene (CTFE) (63) and terpolymers with HEP and tetrafluoroethylene (TEE) (64) (see Elastomers, synthetic-fluorocarbon elastomers). There is intense commercial interest in thermoplastic copolymers of VDE with HEP (65,66), CTEE (67), or TEE (68). Less common are copolymers with trifluoroethene (69), 3,3,3-trifluoro-2-trifluoromethylpropene (70), or hexafluoroacetone (71). Thermoplastic terpolymers of VDE, HEP, and TEE are also of interest as coatings and film. A thermoplastic elastomer that has an elastomeric VDE copolymer chain as backbone and a grafted PVDE side chain has been developed (72). 

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