Polymerization macro

Hence the Norrish II process leads to formation of an alkene [3(a)] or chain scission [3(b)]. The fate of the polymeric macro-radical depends on the sequence distribution of the copolymer. Consider the macroradical ... 

CON Convertine, A.J., Lokitz, B.S., Vasileva, Y., Myrick, L.J., Scales, C.W., Lowe, A.B., and McCormick, C.L., Direct synthesis of thermally responsive DMA/NIPAM diblock and DMA/NIPAM/DMA triblock copolymers via aqueous, room temperature RAFT polymerization, Macro/wo/ecw/es, 39, 1724, 2006. 

Nuyken, O. Meindl, K. Wokaun, A. Mezger, T. A light-sensitive diazosulfonate surfactant as emulsifier for emulsion polymerization. Macro-mol. Rep. 1995, A32, 447 57. 

Recently, Zhao et al. [34,47], and Qiu et al. [21] have reported the graft polymerization of AAM onto macro-... 

Radical polymerizations of macromonomers are greatly influenced by the diffusion control effect [44]. Segmental diffusivity and translational diffusivity of the growing chains of macromonomers are strongly affected by the feed concentration and the molecular weight of the macromonomers. Furthermore, there is little difference in the degree of polymerization between macro-... 

Macro-azo-initiators containing crown ether units were successfully synthesized by Yagci et al. [37,38] condensing ACPC with the c s or trans forms of 4,4 -diaminodibenzo-18-crown-6 (Scheme 8). The polymeric... 

A novel approach to RAFT emulsion polymerization has recently been reported.461529 In a first step, a water-soluble monomer (AA) was polymerized in the aqueous phase to a low degree of polymerization to form a macro RAFT agent. A hydrophobic monomer (BA) was then added under controlled feed to give amphiphilic oligomers that form micelles. These constitute a RAFT-containing seed. Continued controlled feed of hydrophobic monomer may be used to continue the emulsion polymerization. The process appears directly analogous to the self-stabilizing lattices approach previously used in macromonomer RAFT polymerization (Section 9.5.2). Both processes allow emulsion polymerization without added surfactant. 

Many block and graft copolymer syntheses involving transformation reactions have been described. These involve preparation of polymeric species by a mechanism that leaves a terminal functionality that allows polymerization to be continued by another mechanism. Such processes are discussed in Section 7.6.2 for cases where one of the steps involves conventional radical polymerization. In this section, we consider cases where at least one of the steps involves living radical polymerization. Numerous examples of converting a preformed end-functional polymer to a macroinitiator for NMP or ATRP or a macro-RAFT agent have been reported.554 The overall process, when it involves RAFT polymerization, is shown in Scheme 9.60. 

However, the free acid quickly starts to condense with itself, accompanied by the elimination of water to form dimers, trimers and eventually polymeric silicic acid. The polymer continues to grow, initially forming polymer aggregates and then polymer spheres, a few Angstroms in diameter. These polymeric spheres are termed the primary particles of silica gel and must not to be confused with the macro-particles of silica gel that are packed into the LC column. 

In the recent decades, an enzyme-catalyzed polymerization ( enzymatic polymerization ) has been of increasing importance as a new trend in macro-molecular science. Enzyme catalysis has provided new synthetic strategy for useful polymers, most of which are difficult to produce by conventional chemical... 

Acid-base (AB) cements have been known since the mid 19th century. They are formed by the interaction of an acid and a base, a reaction which yields a cementitious salt hydrogel (Wilson, 1978) and offers an alternative route to that of polymerization for the formation of macro-molecular materials. They are quick-setting materials, some of which have unusual properties for cements, such as adhesion and translucency. They find diverse applications, ranging from the biomedical to the industrial. 

Polymer products synthesized in laboratories and in industry represent a set of individual chemical compounds whose number is practically infinite. Macro-molecules of such products can differ in their degree of polymerization, tactici-ty, number of branchings and the lengths that connect their polymer chains, as well as in other characteristics which describe the configuration of the macromolecule. In the case of copolymers their macromolecules are known to also vary in composition and the character of the alternation of monomeric units of different types. As a rule, it is impossible to provide an exhaustive quantitative description of such a polymer system, i.e. to indicate concentrations of all individual compounds with a particular chemical (primary) structure. However, for many practical purposes it is often enough to define a polymer specimen only in terms of partial distributions of molecules for some of their main characteristics (such as, for instance, molecular weight or composition) avoiding completely a... 

Step polymerization is used to synthesize multiblock copolymeric elastomers (referred to as segmented elastomers). An example is the polyester-polyurethane system produced by the reaction of a diisocyanate with a mixture of macro diol and smallsized diol (Eq. 14). The macro diol (usually referred to as a... 

The controlled radical polymerization techniques opened up a new era in polymer synthesis, and further growth and developments are certain. However, the control of the molecular characteristics and the variety of macro-molecular architectures reported by these methods cannot be compared with those obtained by other living polymerization techniques such as anionic polymerization. 

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