Copolymer branch

The polymer may behave as a weak acid ion exchange resin. Branched copolymers have also been proposed as an approach to achieving "smoother" release patterns for polypeptide systems (40). 

This expression differs from Eq. (36) for the weight fraction of x-mer in a simple/-functional condensation chiefly through the replacement of X in the latter by its analog 2(/n —n+1)// for the branched copolymer. 

Branch and bound techniques, discrete optimization via, 26 1023 Branched aliphatic solvents, 23 104 Branched alkylbenzene (BAB), 77 725 Branched copolymers, 7 610t Branched epoxies, 70 364 Branched olefins, 77 724, 726 Branched polycarbonates, 79 805 Branched polymers, 20 391 Branched primary alcohols, synthetic processes for, 2 2 7t Branching... 

A useful approach to detection in polymer HPLC presents the on-line hyphenation of different measurement principles. For example, an RI detector combined with a UV photometer produces valuable additional information on the composition of some copolymers. Further progress was brought with the triple detection RI plus LALS plus VISCO [313], which is especially suitable for branched macromolecules and the tetra detection UV plus RI plus LALS plus VISCO, which enables characterization of some complex polymer systems, exhibiting a distribution not only in their molar mass and architecture, but also in their chemical composition such as long chain branched copolymers. 

Thus, the main problem is how the triple sum in Eq. (C.3) can be evaluated. At first sight, this problem looks formidable. In the following, the techniques of evaluation are described in some detail, starting with the simplest cases of monodisperse homopolymers and proceeding step by step to the more complex molecules of branched copolymers, which are highly polydisperse in molecular weight and heterogeneous in composition. 

Figure 3. Synthetic procedure for the ferrocene-ethylene oxide-siloxane branch copolymers H and I.

The variety of branched architectures that can be constructed by the macromonomer technique is even larger. Copolymerization involving different kinds of macromonomers may afford a branched copolymer with multiple kinds of branches. Macromonomer main chain itself can be a block or a random copolymer. Furthermore, a macromonomer with an already branched or dendritic structure may polymerize or copolymerize to a hyper-branched structure. A block copolymer with a polymerizable function just on the block junction may homopolymerize to a double comb or double-haired star polymer. 

The two principal in-situ syntheses of branched copolymers are by step growth or radical chemistry. It should be noted that crosslinking of the same phase can also occur in addition to branching. This crosslinking is the basic principle of IPN formation. Hence, in this section, we will only refer to reports where crosslinking of the same phase appears to be a side reaction and not the expected one. 

Shih et al. [60] studied the modification of a novolac-type epoxy resin with PDMS to overcome brittleness and poor impact resistance. This kind of resin is typically cured via their epoxy functions. The authors also introduced isocyanate monofunctionalized PDMS. Hence, the common treatment with MDA (4,4 -methylene dianiline) not only cured the resin on the one hand, but also made it possible to form the branched copolymer. Mechanical and thermal analyses showed that an optimum in isocyanate-terminated PDMS content was required to reach good thermal and physical properties and low moisture absorption. 

Graft copolymer—A branched copolymer in which chains made up of one type of repeat unit are bonded to a chain made up of a different repeat unit. 

Fig. 2. Four-arm star branched copolymer with three outer A blocks and two inner B blocks...

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