Comonomer units

Irregularities such as branch points, comonomer units, and cross-links lead to amorphous polymers. They do not have true melting points but instead have glass transition temperatures at which the rigid and glasslike material becomes a viscous liquid as the temperature is raised. 

The carboxylated units, ionized, decrease adsorption on subterranean substrates (23), ia proportion to the number of units, an important parameter ia petroleum recovery processes. In waste treatment processes cationic acrylamide comonomer units are often used (31) to iacrease adsorption and thereby flocculation of soHds ia wastewater (see Acrylamide POLYMERS Flocculating agents). The favorable and characteristics of acrylamide facilitate the... 

Comonomer is exhausted at relatively low conversion (20), but a random copolymer is nevertheless obtained. This is because a very facile transacetalisation reaction allows for essentially random redistribution of the comonomer units (18) and also results in a polydispersity index near 2.0 (21). 

The effect of different types of comonomers on varies. VDC—MA copolymers mote closely obey Flory s melting-point depression theory than do copolymers with VC or AN. Studies have shown that, for the copolymers of VDC with MA, Flory s theory needs modification to include both lamella thickness and surface free energy (69). The VDC—VC and VDC—AN copolymers typically have severe composition drift, therefore most of the comonomer units do not belong to crystallizing chains. Hence, they neither enter the crystal as defects nor cause lamellar thickness to decrease, so the depression of the melting temperature is less than expected. 

Vinyhdene chloride polymers containing stabilizing features have been prepared. In general, these have been polymers containing comonomer units with functionahty that can consume evolved hydrogen chloride and do so in such a manner that good radical scavenging sites are exposed (145,146). 

Morishima etal. [29 — 31] prepared amphiphilic copolymers of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) with various hydrophobic comonomers, and studied the tendency of their self-aggregation and the nature of the hydrophobic microdomains thus formed in aqueous solution. Chart 1 shows some of these amphiphilic copolymers. Here, the value of x indicates the mol% content of hydrophobic comonomer units. 

Change in crystal structure above a certain comonomer content—such that the new crystal stmcture could accommodate comonomer units in the crystal. It is possible that on adding increased amounts of comonmer, the crystal stmcture changes in the commonly observed monoclinic (PP) to a hexagonal stmcture. 

These results confirm that the tendency for an alternating arrangement of the comonomer units increases with the length of alkyl chains at the tin atom. 

The values of K and (3(K > 0 and 0 < P < 1) were calculated for each monomer pair from the logarithmic plot of the ratio of the monomers in the monomer feed [MJ/[M2] to the comonomer units in the copolymer using a modified equation of binary copolymerization ... 

A considerable viscosity increase in copolymers of tributylstannyl methacrylate with methyl methacrylate, butyl acrylate and styrene upon prolongated storage has been observed and special agents to eliminate this effect have been proposed 108). It is likely that the destruction of intermolecular coordination complexes formed by involvement of tin and carbonyl groups in comonomer units takes place in this case. 

For the copolymers, the stabiliser is less affected during accelerated ageing due to the presence of the comonomer units. 

Poly(HASCL) (i.e. PHB and poly(3HB-co-3HV)) are typical thermoplastic polymers, which become fluid and moldable above their melting points, whereas poly(HAMCL)s generally are elastomers with low melting points. PHB has been reported to show a relatively high melting temperature of about 180°C, while the Tg of this polymer is approximately 9 °C [21,52,53]. Incorporation of 3HV-comonomer units into PHB decreases both the Tm as well as the Tg significantly. Poly(3HB-co-3HV), containing up to 28 mol% 3HV, has a Tm of about 102°C and a Tg of -8°C, respectively [21,52,53]. 

Abstract Protein-like copolymers were first predicted by computer-aided biomimetic design. These copolymers consist of comonomer units of differing hydrophilicity/hydro-phobicity. Heterogeneous blockiness, inherent in such copolymers, promotes chain folding with the formation of specific spatial packing a dense core consisting of hydrophobic units and a polar shell formed by hydrophilic units. This review discusses the approaches, those that have already been described and potential approaches to the chemical synthesis of protein-like copolymers. These approaches are based on the use of macromolecular precursors as well as the appropriate monomers. In addition, some specific physicochemical properties of protein like copolymers, especially their solution behaviour in aqueous media, are considered. 

Nonetheless, one cannot exclude the probability of a successful combination of these prerequisites (as was the case with poly[(NiPAAm-co-GMA)-g-PEO considered above]) that will allow us to obtain, using the chemical colouring approach, the protein-like HP-copolymers with a dense hydrophobic core wrapped by the hydrophilic shell. Such a shell should be capable of efficiently protecting the temperature-responsive macromolecules against pronounced interchain hydrophobic interactions and precipitation at temperatures significantly higher than those at which the copolymers of the same total monomer composition—but with a non-protein-like primary sequence of comonomer units—are in the soluble state. 

Due to higher variety of possible structures, copolymers allow a better control of the HOMO LUMO levels necessary to optimize the EL properties of the PPV, compared to homopolymers. Often the optical and electronic properties in copolymers can be finely tuned by simply changing the feed ratio of comonomers (although the structure-property relationship in these systems is even more complex than in homo-PPV polymers). Using different comonomer units, various PPV-based materials with tuned optical and electronic properties have been prepared. 

Copolymers with Three or More Comonomer Units... 

A special case of asymmetric enantiomer-differentiating polymerization is the isoselective copolymerization of optically active 3-methyl-1-pentene with racemic 3,7-dimethyl-1-octene by TiCl4 and diisobutylzinc [Ciardelli et al., 1969]. The copolymer is optically active with respect to both comonomer units as the incorporated optically active 3-methyl-l-pentene directs the preferential entry of only one enantiomer of the racemic monomer. The directing effect of a chiral center in one monomer unit on the second monomer, referred to as asymmetric induction, is also observed in radical and ionic copolymerizations. The radical copolymerization of optically active a-methylbenzyl methacrylate with maleic anhydride yields a copolymer that is optically active even after hydrolytic cleavage of the optically active a-methylbenzyl group from the polymer [Kurokawa and Minoura, 1979]. Similar results were obtained in the copolymerizations of mono- and di-/-menthyl fumarate and (—)-3-(P-styryloxy)menthane with styrene [Kurokawa et al., 1982],... 

The surface of polymer particles obtained by emulsion polymerization is occupied by emulsifier molecules, initiator fragments, and hydrophilic comonomer units. Therefore, desirable design of the surface ought to be done by choosing the emulsifier, initiator, and comonomer. Some of them are employed in aiming for postreaction at the surface to convert it into a functional one. When any change is necessary on the particle surface, modification of surface can be done by the following means ... 

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