Polymeranalogous reactions

Polymeranalogous reactions considered above may be referred to as intramolecular condensation transformations since they are accompanied by elimination of low-molecular products. On the other hand, PCSs can be obtained via polymeranalogous transformations, principally intramolecular polymerization reactions . Thermal and chemical cyclization of poly(acrilonitrile) (PAN) is an example of processes of this type. It was demonstrated by a number of researchers216-225 that thermal transformations of PAN follow the scheme  

Phenols, alkali225, and some other substances226-228 serve as initiators of these reactions. In the case of poly(acrylonitrile) this role is played by a tertiary hydrogen which is activated by the C=N group. 

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Keywords Chemical structure of macromolecules Free-radical copolymerization Polymeranalogous reactions... 

Presently, the quantitative theory of irreversible polymeranalogous reactions proceeding in a kinetically-controlled regime is well along in development [ 16,17]. Particularly simple results are achieved in the framework of the ideal model, the only kinetic parameter of which is constant k of the rate of elementary reaction A + Z -> B. In this model the sequence distribution in macromolecules will be just the same as that in a random copolymer with parameters P(Mi ) = X =p and P(M2) = X2 = 1 - p where p is the conversion of functional group A that exponentially depends on time t and initial concen-... 

In order to estimate the region of this approximation applicability, it is necessary to examine macrokinetics of a polymeranalogous reaction with explicit allowance for the diffusion of a reagent Z into a globule. In this case, the profile of its constituent monomeric units will be fuzzy rather than stepwise (see Fig. 1). This brings up two questions. The first one is how this profile depends on kinetic and diffusion parameters of a reaction system. The second question is concerned with the effect of the profile shape on the statistical characteristics of the chemical structure of the products of a polymeranalogous reaction. A rigorous theory has been developed [22,23] which enables us to answer these questions. The main concepts of this theory are outlined in the subsequent Sections. 

Fig. 5 Comparison of phase diagrams calculated for the melt of a proteinlike heteropolymer (b) with the phase diagram of a Markovian copolymer according to criterion II (a) and criterion I (c). Proteinlike heteropolymer consisting of / = 103 units is obtained for polymeranalogous reaction in a homopolymer globule at the value of the Thiele modulus h equal to 35... 

This method may be used when the structure of the drug is stable during the polymerization process. An advantage of this method is the avoidance of side-reactions which sometimes occur during polymeranalogous reactions. Examples of earlier studies may be found in reviews [20, 140], some recent examples follow. 

Block copolymers with liquid crystalline side chains were investigated for the first time by Adams and Gronski in 1989 [60], A polymeranalogous reaction was used to attach the mesogenic side-groups to one of the blocks. In a similar way, block copolymers with azobenzene chromophores were synthesized by Ober et al. [43, 44], In the scope of this review the synthesis of azobenzene-containing block... 

Polymeranalogous reaction with activated side-groups... 

Fig. 4 General synthetic strategy to obtain block copolymers with azobenzene-containing side-groups via polymeranalogous reaction (open circles) protected functional groups, (filled circles) functional groups, (rectangles) azobenzene chromophore units...

Subsequently the polybutadiene segment was functionalized by quantitatively converting the olefin double bonds of the 1,2-polybutadiene block via a hydroboration reaction to hydroxyl functions. In the last step various azobenzene-chromophores were attached via a polymeranalogous reaction. The synthesis and characterization as well as photophysical aspects of block copolymers based on an amorphous polystyrene block and a functionalized 1,2-polybutadiene block... 

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