Poly different conditions

Polyacrylates are an industrially important class of polymers. The name polyacrylate is variously used to refer to polymers of acrylate esters [e.g., poly(methyl methacrylate)] as well as polymers of acrylic acids [e.g., poly(meth-acrylic acid)]. Because the former is organic soluble while the latter is not, chromatographic analysis of these two requires quite different conditions. This chapter discusses both types of polymers, separating their consideration when necessary. We will refer to both types of polymers as polyacrylates, letting the context indicate whether we are referring to an ester or to an acid polymer. 

FIGURE 24.4 Master curves of the local segmental relaxation times for 1,4-polyisoprene (-y = 3.0) 1,2-polybutadiene (7=1.9) polyvinylmethylether (7 = 2.55) polyvinylacetate (7 = 2.6) polypropylene glycol (7 = 2.5) polyoxybutylene (7 = 2.8) poly(phenyl glycidyl ether)-co-formaldehyde (7 = 3.5) polymethylphe-nylsiloxane (7 = 5.6) poly[(o-cresyl glycidyl ether)-co-formaldehyde] (7 = 3.3) and polymethyltolylsiloxane (PMTS) (7 = 5.0) [15 and references therein]. Each symbol for a given material represents a different condition of T and P. 

Extensive data are given in the Uterature for the potentiometric titration of polymer acids which may be used to study the behaviour of polyelectrolyte systems under different conditions. For poly(a-D) galacturonic acid there are few data of this kind, especially in connection with the occurrence of a conformational transition induced by pH variations, or with the effect brought about by the addition or the exchange of counterions. Since for a polyacid not exhibiting a conformational transition in the course of titration, pK K denoting the apparent dissociation constant) increases monotonously with degree... 

The conformations adopted by polyelectrolytes under different conditions in aqueous solution have been the subject of much study. It is known, for example, that at low charge densities or at high ionic strengths polyelectrolytes have more or less randomly coiled conformations. As neutralization proceeds, with concomitant increase in charge density, so the polyelectrolyte chain uncoils due to electrostatic repulsion. Eventually at full neutralization such molecules have conformations that are essentially rod-like (Kitano et al., 1980). This rod-like conformation for poly(acrylic acid) neutralized with sodium hydroxide in aqueous solution is not due to an increase in stiffness of the polymer, but to an increase in the so-called excluded volume, i.e. that region around an individual polymer molecule that cannot be entered by another molecule. The excluded volume itself increases due to an increase in electrostatic charge density (Kitano et al., 1980). 

Rather recently, we have studied the solid-state structure of various polymers, such as polyethylene crystallized under different conditions [17-21], poly (tetramethylene oxide) [22], polyvinyl alcohol [23], isotactic and syndiotactic polypropylene [24,25],cellulose [26-30],and amylose [31] with solid-state high-resolution X3C NMR with supplementary use of other methods, such as X-ray diffraction and IR spectroscopy. Through these studies, the high resolution solid-state X3C NMR has proved very powerful for elucidating the solid-state structure of polymers in order of molecules, that is, in terms of molecular chain conformation and dynamics, not only on the crystalline component but also on the noncrystalline components via the chemical shift and magnetic relaxation. In this chapter we will review briefly these studies, focusing particular attention on the molecular chain conformation and dynamics in the crystalline-amorphous interfacial region. 

Table 1. Structure of poly(l,4-anhydro-2,3,6-tri-0-benzyl-a-n-glucopyranose) prepared under different conditions [28]...

Abstract Investigations of alternate adsorption regularities of cationic polyelectrolytes a) copolymer of styrene and dimethylaminopropyl-maleimide (CSDAPM) and b) poly(diallyldimethylammonium chloride) (PDADMAC) and anionic surfactant - sodium dodecyl sulfate (SDS) on fused quartz surface were carried out by capillary electrokinetic method. The adsorption/desorption kinetics, structure and properties of adsorbed layers for both polyelectrolytes and also for the second adsorbed layer were studied in dependence on different conditions molecular weight of polyelectrolyte, surfactant and polyelectrolyte concentration, the solution flow rate through the capillary during the adsorption, adsorbed layer formation... 

The rapid and quantitative displacement of phenyl groups from model silanes suggests that similar reactions with aryl-substituted polysilanes should lead to the triflated polymer. We have carried out this displacement under different conditions. Approximately the first 80% of the phenyl groups were removed rapidly from poly(phenylmethylsilylene). No free acid was observed... 

Rather recently, we have studied the soUd-state structure of various polymers, such as polyethylene crystallized under different conditions [17-21], poly (tetramethylene oxide) [22], polyvinyl alcohol [23], isotactic and syndiotactic polypropylene [24,25],cellulose [26-30],andamylose [31] with solid-state high-resolution NMR with supplementary use of other methods, such as X-ray dif-... 

In the same way, Oishi et al. [256] used IEM to functionalize oligomers carrying an acid function obtained by polymerization of chiral acrylamides. Chiral polyacrylamide macromonomers were synthesized from 2-methacryloyloxyethyl isocyanate and prepolymers, i.e., poly[(S)-methyl-benzyl acrylamide] or poly(L-phenylalanine ethylester acrylamide) with a terminal carboxylic acid or hydroxyl group. Radical homopolymerizations of polyacrylamide macromonomers were carried out under different conditions to obtain the corresponding optically active polymers, as shown in Scheme 52. 

Finally, Chiefari et al. [315-317] suggested another technique leading to the synthesis of addition-fragmentation-type macromonomers but without the use of any CTA. This method, clean, easy, and economical, involves heating a mixture of acrylate or styrene monomer in an appropriate solvent with an azo or peroxy initiator. High temperatures (typically up to 150 °C) are required. To prove the expected mechanism, the authors studied the poly(alkyl acrylate) reactions in the presence (or not) of monomers and by using different conditions. They showed the reaction does not occur without the monomer. Moreover, an increase of the temperature leads to a better yield and a decrease of the molar mass. Macromonomers have been synthesized by this technique withMn between 103 and 104 gmol... 

Figure 6. Temperature dependence of optical transmittance for poly(NIPAAm-co-Ru(bpy)3) solutions under the different conditions of reduced Ru(II) state (in Ce(lll) solution) and oxidized Ru(III) state (in Ce(IV) solution). (Reproduced from reference 25. Copyright 2002 American Chemical Society.)...

Figure 3.2 shows crystallization of poly(lactic acid) under different conditions. If PLA does not contain nucleating agents, crystallization is slow and produces only a few spherulites. If too small amount Figure 3.2. Polarized optical microscopy photographs of of nucleating agent is added, crystallization (a), pla containing 0.05 wt% hydrazide...

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