Daughter chains

Fig. 8 Schematic representation of the synthetic approaches of stem and branch designs. Model A is prepared under a fixed parent-chain length but different daughter-chain lengths. Model B is prepared under a fixed daughter-chain length but different parent-chain lengths. Model C is prepared under fixed parent-chain and daughter-chain length but different daughter-chain densities...

Variable Parent Chain Lengths and Variable Daughter Chain Lengths... 

Fig. 9 Top Rose-bengal-stained fluorescence images of photograft-polymerized regions of Models Ay B and C as a function of photopolymerization time or copolymer composition of CMS (see Fig. 8 legend). These indicate that stem-chain length (Model A), daughter-chain length (Model B) and daughter-chain density (Model C) are well-controlled. Bottom Change in fluorescence intensity as a fimction of photopolymerization time or copolymer composition of CMS CMS Chloromethyl styrene...

Systems are considered in which, under certain conditions, matrix regeneration is possible in the process of matrix synthesis (i.e. freeing of the matrix from the polycomplex being formed) and multiple use of a single matrix for controlling the growth of the daughter chains. 

Since no information can be passed from the matrix to the daughter chain without holding the growing chain on the matrix, the matrix polymerization takes place only provided the chain lengths of the matrices and the daughter chains are not shorter than is necessary to form a stable polycomplex between them. 

In a very simple case, matrices play the role of microreactors creating a reaction medium near the active ends of the growing macromolecules which differs from that in the rest of the solution. For example, for matrix polymerization of MA on PEO macromolecules, the stereostructure of the PM A daughter chains is similar both in water and in benzene in fact, it is the same as for polymerization of MA without matrix in alcohol media24 . Probably, this is determined by the fact that the dielectric permetivity in the microreactor, where the active centre of the... 

Under copolymerization, the preferred sorption of one of the monomers on the matrix leads to enriching the daughter chains with this monomer. For instance, Polovinsky showed that MA — methyl methacrylate 85) and MA-styrene 86) copolymers, formed in the presence of a PEO matrix, are enriched in MA, the constants of copolymerization depending on the concentration of the matrix. It is shown by Kargina et al. 87) that in the presence of a PPh-Na matrix copolymers of 2-methyl-5-vinylpyridine and AA are considerably enriched in the cation monomer up to complete elimination of AA and formation of homopoly-2-methyl-5-vinylpyridine. 

The influence exerted by the matrix on the direction of the elementary growth steps of the daughter chains was observed for the matrix polymerization of 4PV on polyacids when the daughter P4VP had ionene structure 81), and for the matrix polycondensation of urea and formaldehyde in water, with PAA being present 88,89). In the latter case, the daughter chains of PFU contained the structures... 

However, no matter how rigidly the matrix controls the structure of the daughter chain, the latter will always contain a fragment or fragments formed independently of the matrix, i.e., before its recognition . 

For matrix polymerization, the fraction of such fragments depends on the correlation between the length of the matrix and of the daughter chain. If the length of the daughter chain corresponds to that of the matrix, as, for example, for... 

Since the polycomplex is a product of matrix polymerization or polycondensation, each macromolecule of the matrix works as a matrix only once. All attempts to create systems with the workable zip-up mechanism of polymerization of monomer molecules, preliminarily bound with the matrix, with automatic liberation of the formed daughter chain from the matrix, have ended in failure (this was assumed to be possible, when, for instance, stabilization of the monomer-matrix complex takes place due to the presence of the double bond in the monomer 94 95>. 

Such reaction systems must include, besides monomers (or comonomers), relatively short chains of the strong matrix and long chains of the weaker matrix. Further, after the end of the growing chain has reached the end of the chain of the strong matrix, the chain-growth does not end, i.e., the growth of the daughter chain continues in accordance with Scheme 13 b. 

Thus, a cooperative interaction of the growing daughter chain with the mac-romolecular matrix is possible only when a critical degree of polymerization n. of the... 

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