Poly statistical copolymers

Common rubbery materials consist of butadiene and styrene statistical copolymers, written poly(butadiene-sfaf-styrene). The butadi-... 

The endopolygalacturonase obtained from a Kluyveromyces marxianus culture broth was purified through the addition of specifically designed core-shell microspheres consisting of an inner polystyrene core and an outer shell constituted by a poly(methacrylic acid-co-ethylacrylate) statistical copolymer. These microspheres were previously found very effective in purifying the pectinlyase within a commercial pectinase sample [15]. 

Wang, R, Hickner, M., Kim, Y. S., Zawodzinski, T. A. and McGrath, J. E. 2002. Direct polymerization of sulfonated poly(arylene ether sulfone) random (statistical) copolymers Candidates for new proton exchange membranes. Journal of... 

Statistic copolymer Poly(A-stot-B) e.g., Poly(styrene-stflf-butadiene)... 

Abstract The formation of stable metal/polymer joints is an enormous challenge in material sciences. Good adhesion requires an interphase which is able to specifically interact with the metal substrate as well as with the second component. Furthermore, the interphase should compensate thermally generated mechanical tensions between the two adhering components. It will be shown that statistic copolymers of poly(vinyl formamide) and poly(vinyl amine) (PVFA-co-PVAm) are potential candidates for adhesion promoters. The polyelectrolyte character of the copolymers allows to apply them from its aqueous solutions. The primary amino groups exhibit the copolymers as highly reactive to metal surfaces as well as to the second joint partner. The... 

Thus a statistical copolymer of ethylene and propyiene is named poly(ethylene-stef-propylene), and an ABA tri-block copolymer of styrene (A) and isoprene (B) is named polystyrene-block-polyisoprene-block-polystyrene. In certain cases, additional square brackets are required. For example, an alternating, copolymer of styrene and maleic anhydride is named poly[styrene-d/f-(maleic anhydride)]. 

In statistical copolymers the sequence of monomeric units obeys some known statistical law, e. g. Markov statistics of zero order (Bernoulli), or of the first, second or higher orders. Such copolymers are designated as poly (M,-,yfaf-M2-sfaf- M, -- ) [3]. 

Recently, the orientation behavior of poly-(IV-5) was compared to both poly-(IV-4) and a statistical copolymer poly-IV-5-COEN (COEN=cyclooctene) [51]. The experiments shotved that, compared to poly-(IV-5), samples of poly-(IV-5-COEN) were easier to orientate, a finding that was attributed to the more flexible chain. The dependence of the magnetic field and the temperature on the degree of orientation, measured by the birefringence and the optical transparency, is shown in Fig. 6. 

The same group reported on the synthesis and characterization of all-hydrocarbon MCLCPs, poly-(XXXX), and their hydrogenated derivatives poly-(XXXXI), based on 4,4 -bis(a-co-alkenyl)-l,r-biphenyl derivatives, see Fig. 23. Monomers with different a-co-alkenyl chain lengths were used to prepare not only the corresponding homopolymers but also statistical copolymers. Crystallinity, thermal transition properties and LC properties were studied. 

Polymers and copolymers were laboratory-prepared samples. Samples W4 and W7 of the diblock copolymer AB poly(styrene-fo-tetramethylene oxide) (PS—PT) were synthesized by producing a polystyrene prepolymer whose terminal group was transformed to a macroinitiator for the polymerization of THF. Samples B13 and B16 of the diblock copolymer AB poly[styrene-h-(dimethyl siloxane)] (PS-PDMS) were prepared by sequential anionic polymerization. Samples of statistical copolymers of styrene and n-butyl methacrylate (PSBMA) were produced by radical copolymerization. Details of synthetic and characterization methods have been reported elsewhere (15, 17-19). 

Novel approaches in PEM synthesis focusing on cheaper, usually fluorine-free PEMs and membranes capable of sustained fuel cell operation at elevated temperatures, have been reviewed in Ref. 75. Mature fuel cell membranes have been casted from sulfonated poly(arylene ether sulfone) (BPSH) random (statistical) copolymers [76]. 

In the proceeding sections, emphasis has been placed on pH-responsive homopolymers whose conformational behavior is dictated by the hydrophobic to hydrophilic balance within the system. The switch in conformation is marked by a change in macroscopic properties, such as solution viscosity, over a narrow and characteristic pH range specific to that polymer which is important from a technological viewpoint. Manipulation of the switch to any desired pH has attracted much interest in the literature because this could lead to many more potential applications for the modified poly electrolyte. Synthetic strategies adopted to achieve this end have included simple copolymerization of an ionizable repeat unit with a hydrophobic monomer [20,27—43,1291 to form statistical copolymers and formation of block copolymers [71,158-180]. (A block copolymer consists of sequences of monomers A and B such as -(A) -(B)m or -(A) -(B)m-(A) , where n and m represent the number of repeat units.)... 

Block Copolymers. Several methods have already been used for the synthesis of block copolymers. The most conventional method, that is, the addition of a second monomer to a living polymer, does not produce the same spectacular results as in anionic polymerization. Chain transfer to polymer limits the utility of this method. A recent example was afforded by Penczek et al. (136). The addition of the 1,3-dioxolane to the living bifunctional poly(l,3-dioxepane) leads to the formation of a block copolymer, but before the second monomer polymerizes completely, the transacetalization process (transfer to polymer) leads to the conversion of the internal homoblock to a more or less (depending on time) statistical copolymer. Thus, competition of homopropagation and transacetalization is not in favor of formation of the block copolymers with pure homoblocks, at least when the second block, being built on the already existing homoblock, is formed more slowly than the parent homoblock that is reshuffled by transacetalization. 

The stracture-property correlation of different copolymers with n-butyl acrylate and isobomyl acrylate units have been studied. The primary goal was to compare thermomechanical properties of block, gradient and statistical copolymers of nBA and IBA with various acrylate homopolymers (Scheme 1). The choice of nBA and IBA was dictated by very different thermal properties of the resulting homopolymers, glass transition temperature (Tg) of PnBA is -54°C while the Tg of PIBA is 94°C. Thus, their copolymerization with carefully selected ratios should result in polymers with thermal properties, i.e., Tg similar to acrylate homopolymers poly(t-butyl acrylate) (PtBA), poly(methyl acrylate) (PMA), poly(ethyl acrylate) (PEA) and poly(n-propyl acrylate) (PPA). 

Optical densities at 269.5 nm for polystyrene solutions at concentrations of 0-1 X 10"2 mole/liter and for poly(styrene-co-methyl methacrylate) solutions at a total concentration of 1 X 10 2 mole/liter are presented in Figure 1 as functions of styrene content. The solvents were (from the top) dioxane, chloroform, tetrahydrofuran (THF), tetrachloroethane (TCE), and dichloro-ethane (DCE). It is evident that the linear relationship between optical density and styrene concentration that is valid for a polystyrene at all concentrations (open circles) does not hold for the statistical copolymers (solid circles). For example, copolymer (25-80 mole % styrene) solutions in chloroform deviate markedly from linearity the maximum per cent decrease in extinction coefficient (hypochromism) corresponds to a copolymer containing 50 mole % styrene. We define hypochromism as the decrease in absorption intensity at 269.5 nm per chromophore of the statistical copolymer relative to that of the atactic polystyrene. It is also evident from Figure 1 that the alternating copolymer also gives a sharp hypochromism whereas block copolymers and mechanical mixtures of polystyrene and poly (methyl methacrylate) do not deviate from the straight line. Similar results were obtained with the other solvents, but the composition range where hypochromism appears depends on the solvent used. 

The solidus denotes an unspecified arrangement of the units within the main chain. " For example, a statistical copolymer derived from styrene and vinyl chloride with the monomeric units joined head-to-tail is named poly(l-chloroethylene/l-phenyleth-ylene) . A polymer obtained by 1,4-polymerization and both head-to-head and head-to-tail 1,2- polymerization of 1,3-butadiene would be named poly(but-l-ene-l,4-diyl/l-vinylethylene/2-vinyl-ethylene) In graphic representations of these polymers, shown in Figure 2, the hyphens or dashes at each end of each CRU depiction are shown completely within the enclosing parentheses this indicates that they are not necessarily the terminal bonds of the macromolecule. 

Statistical copolymers are those in which the monomer sequence follows a specific statistical law (e.g., Markovian statistics of order zero, one, two). Random copolymers are a special case of statistical copolymers in which the nature of a monomeric unit is independent of the nature of the adjacent unit (Bernoullian or zero-order Markovian statistics). They exhibit the structure shown in Figure 6.1. If A and B are the two monomers forming the copolymer, the nomenclature is poly (A-stat-B) for statistical copolymers and poly (A-ran-B) for the random case. It should be noted that sometimes the terms random and statistical are used indistinctly. The commercial examples of these copolymers include SAN poly (styrene-ran-acrylonitrile) [4] and poly (styrene-ran-methyl methacrylate) (MMA) [5]. 

Lambe et al. (1978) studied the enhanced steric stabilization of polystyrene latices by poly(vinyl alcohol). This is included in this sub-section on copolymers because the samples studied were not fully hydrolysed. This means that the parent poly(vinyl acetate) from which they were derived was only partially (88%) hydrolysed (this is often accomplished by alcoholysis). The resultant polymer is not, however, a completely random copolymer because adjacent group effects influence the hydrolysis kinetics in such a way that some degree of blockiness is introduced. On average, these blocks consist of 2 ester groups to every 18 alcohol groups but blocks of average size 5-6 acetate groups are common. The chemical structure of the polymers should therefore formally represented by a structure intermediate between poly(vinyl acetate-6-vinyl dcohol) and poly(vinyl acetate-co-vinyl alcohol) rather than poly(vinyl alcohol) as such. The random (or statistical) copolymer can be prepared by partial reacetylation of fully hydrolysed poly(vinyl alcohol). 

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