Copolymers with Partial Substitution

Although this partial chain degradation phenomenon is a problem, these results are nevertheless interesting as the chemical modification route affords easy access to otherwise inaccessible copolymers with fully substituted carbon atoms adjacent to the sulfone functionalities. It is expected that changes in reaction conditions might result in less degradation of the poly(styrene sulfone) chains. Approaches toward this goal are under study. 

From Tg dependence on dimethylsiloxane unit length, indicates that the increase of Tg of copolymers with the number of phenyl groups and volume of cyclic fragment. Partial substitution of methyl groups at silicon atom in silsesquioxane fragment by phenyl ones will increase Tg by 10°C. Similar dependence was detected for all copolymers with cyclic fragments in dimethylsiloxane backbone. 

A system similar to the partially substituted poly(vinylalcohol) was proposed by Penner et al. Thty prepared copolymers of a mesogenic azobenzene monomer and hydroxyethylacrylate (HEA) 34 with different compositions. 

One way to modify PPP is to prepare copolymers with only partial substitution. Jing et al. (1994) prepared a random copolymer (Chaturvedi et al. 1992) with 33% of unsubstituted phenylene units by copolymerization of the substituted and unsubstituted bromobenzene boronic acids. Copolymers (Tanigaki et al. 1996) with alternating substituted and unsubstituted phenylenes were obtained by Stille (Bao and Yu 1995 Savenkova et al. 2000) or Suzuki coupling, both resulting in reduction of brittleness of PPP. 

One way to red shift the emission is to make copolymers with only partial substitution. Hohnes and coworkers prepared the random copolymer 49 with 33% of unsubstituted phenylene units (m = 2 1) by copolymerisation of the substituted and unsubstituted bromobenzene boronic acids (Scheme 20) [75]. The PL emission was blue (A,max 420 nm), but the EL was... 

Partial substitution of terephthalate-based polymers with the naphthalate group, in a copolymer or blend form, can provide enhanced properties that are... 

Kataoka K, Ishihara A, Harada A, Miyazaki H (1998) Effect of the secondary structure of poly (L-lysine) segments on the micellizatimi in aqueous milieu of poly(ethylene glycol)- oly (L-lysine) block copolymer partially substituted with a hydrocinnamoyl group at the JV-epsilon-positioiL Macnnnolecules 31 6071-6076... 

For technical application of this partially substituted alternating copolymer of hexuronic acid and glucosamine some investigations were performed to develop more effective alternatives to the complicated and expensive isolation procedure of ES-HS from primary cell cultures of bovine aortic endothelial cells. Since the lung is the organ with the highest content of endothelial cells and the largest blood contact surface it was chosen for the isolation of ES-HS. 

It was found that in spite of the large excess of modifying amine (N-isopropyl-, -diethyl, -dipropyl, -diisopropyl, -n-hexyl, -cyclohexyl, -n-octyl), the extent of substitution did not exceed 5-10 molar %. For the case of the N-isopropyl derivative, i.e. [poly(AAm-co-NiPAAm)], the authors connected such results with the temperature-induced conformational transformation of partially hydrophobized copolymer acquiring the contracted conformation, "... which made it difficult for N-isopropylamine to react further with the amide groups [22], Unfortunately, no data on the solution behaviour of these interesting copolymers have been reported to date, although there is a high probability that they would demonstrate certain properties of the protein-like macromolecules. At least, in favour of similar supposition is supported by the results of our studies [23] of somewhat different PAAm partially hydrophobized derivative, whose preparation method is depicted in Scheme 3. 

Unit distribution in the substituted PMMA (35) was investigated by two independant methods a) Direct analysis of copolymer microstructure by H-NHR at 250 MHz the NMR spectrum (pyridine solution at 80°C) are sufficiently well resolved to allow a quantitative analysis of unit distribution, in terms of A centered triads and isolated B units in ABA triads, b) UV studies of the ionization and of the intramolecular cyclization of the B B and B B dyads in protic basic media (Na0H-H 0 O.IN, NaOMe-MeOH O.IN) in such a medium the partially ionized copolymer chains are the site of a complex series of consecutive intramolecular reactions we have completely elucidated (35). The first step is of interest with respect to B unit distribution ... 

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