Intrapolymer

The formation of inter- and intrapolymer complexes has also been shown to affect the polymerization kinetics. For example, Ferguson and Shah (1968) investigated the influence of intrapolymer complexation on the kinetics of AA in the presence of copolymer matrices composed of either A-vinylpyrrolidone and acrylamide or A--vi nyl pyrrol idone and styrene. The polymerization rate reaches a maximum in the vicinity of AA to VP ratio equal to one for the VP/AAm matrix. This maximum in the polymerization rate is most pronounced in the presence of copolymer with the highest content of VP. When the hydrophilic acrylamide is replaced with the more hydrophobic styrene monomer in the copolymer matrix, the observed maximum in AA polymerization rate occurred at a lower than equimolar ratio of AA to VP. The hydrophilic groups of VP were interacting with the hydrophobic nucleus consisting of the styrene units in the VP/St copolymer, and were thus unable to participate in the formation of the complex unlike in the case of VP/AAm copolymer matrix. 

Polymeric phosphin-Ni complex also has a selectivity in its catalytic activity (154). Such a sterically selectivity is shown in an intrapolymer electrophilic reaction of Fe-carbonyl-olefin complex (155,156). 

Section B is representative of C-C and C-O cleavage at the intrapolymer level which cannot be recovered. Examples of C-C bond breakage are lignin-hemicellulose copolymer separation, hemi-cellulose depolymerization, and amorphous cellulose depolymerization. 

What causes the phenomenon of stress and strain reduction and why is the reduction in impact and work properties so visible at small or negligible changes in elastic modulus and ultimate strengths As discussed previously, mechanical properties deal with stress and strain relationships that are simply functions of chemical bond strength. At the molecular level, strength is related to both covalent and hydrogen intrapolymer bonds. At the microscopic level, strength... 

The critical pH for bulk phase separation seems to be significantly larger than the pH at which intrapolymer complexes are first formed, and the aggregation of molecular complexes appears as an intermediate process. One may speculate that, near the isoelectric point of the protein (ca. 4.8 for BSA), each polyion chain binds some number of proteins which depends on polymer chain length and flexibility, and also upon protein dimensions. The net charge of this complex, however, remains positive until the pH substantially exceeds the isoelectric point. Under such conditions, intrapolymer complexes may begin to associate. 

Azegami S., Tsuboi A., Izumi T., Hirata M., Dubin P. L., Wang B., Kokufuta E. Formation of an intrapolymer complex from human serum albumin and poly(ethylene glycol). Langmuir 1999 15 940-947. 

Chemical transformations of polymers always include the possibility of undesired modifications which are difficult to recognise but might be responsible for low yields or purity of products if such polymers are used as reagents. Examples of intrapolymer reactions leading to additional crosslinking have been discussed in the previous chapter. 

Chemical structure is taken into account via the structural matrix, Wp(r), composed of the partial intrapolymer site-site distribution functions, Wap r). The elements of Wp(r) are given by Waaf) = Pa aaf) and Waiif) = PpWaisf), where... 

For low MW salts, K eC nd its ionic strength dependence are primarily determined by solute-substrate interactions, usually electrostatic, including the Donnan equilibrium between the mobile phase and the gel phase. Deviation from Kv ec = 1 can be attributed with confidence to such effects. For polyions, the "ideal" or "unperturbed" value of K jeC ( °eC difficult to identify furthermore, because of intrapolymer repulsion and concommitant chain expansion (30), itself is dependent on ionic strength. Consequently, derivations from ideal SEC due to charge interactions may go undetected, and possibly only the more dramatic cases are recognized in the literature. 

Hydrophobic association is also enhanced in polymer systems. Although polymer surfactants are considered to form micelles via intrapolymer hydrophobic interaction, our recent study (2r,s) revealed that a polyionene bearing anthryl groups as the hydrophobic domain showed a clear cmc UHtical micelle concentration) at the segment concentration around 3 x 10 5m. Reference experiments with a polyionene without anthryl groups and the monomer and dimer model compounds have indicated that the cmc is particularly low for the polymer. Taking the excimer intensity of anthracene fluorescence as an index of interchromophore interaction, we confirmed the existence of interpolymer association by the concentration dependent excimer intensity. Under the same condition to the polymer, any model systems either monomeric or dimeric do not associate intermolecularly. 

The interpolymer association is a distinctively different property of exciplex forming polymers from that of excimer forming polymers. The reason must be attributed to the presence of the ground state interaction in the former polymers. Interpolymer excimer formation is, however, facilitated by the aid of hydrophobic interaction in water. Polyionenes bearing anthryl groups (J2) form both inter- and intrapolymer excimer in water (2s). The excimer intensity decreases with increasing hydrophobic interaction. All experimental results indicate that weak intermolecular interactions almost undetectable in small molecule systems are amplified enormously in polymer systems in dilute solutions. 

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