Polymer chain contraction

The conformations of tethered polyethylene glycol (PEG) chains anchored on styrene polymers (PS) latex particles, labelled with pyrene and mononaphthyl PEG ester, in the presence of an anionic surfactant, dodecyl sulphate (SDS), and Na and K chlorides were studied, using distance-dependent nonradiative energy transfer from the naphthalene moieties to the pyrene ones as a guide. The results indicated a change in acceptor/donor separation distance in response to external stimuli. Analysis of the resnlts snggested considerable polymer chain contraction on interaction with salts and surfactant below the critical micelle concentration of the surfactant. 

Fig.l7 Schematic illustration of a single polymer chain contracted in a two-dimensional monolayer. Reprinted with permission of [26], copyright (2003) The Chemical Society of Japan... 

Figure 4.18. The polymer chain contracts with an increasing concentration becanse of shielding of excluded volume. The radius of gyration decreases in a power of monomer density p with an exponent of -1/8.

Ion binding reduces the repulsive forces between the charged groups on the polyanion but, unless the counterions are site-bound, the repulsive osmotic forces are not affected. At full neutralization the coulombic forces along the polymer chain become zero. However, the polymer does not contract, because the osmotic forces remain unless, of course, all the cations become site-bound. (Of course, in the case of a free weak acid the concentration of mobile hydrogen ions is very small and the polymer adopts a compact form.)... 

In order to study the shape of a polymer-Cu complex, viscometric measurements of a homogeneous solution of QPVP were carried out (Fig. 1). At constant QPVP concentration, an increase in the added amount of Cu ions causes a decrease in viscosity, which reveals that the polymer-ligand chain is markedly contracted due to intra-polymer chelation. An intra-polymer chelate takes a very compact form and Cu ions are crowded within the contracted polymer chain (Scheme 2). The adsorption of Cu ions on the polymer ligand is sigmoidal, as can be seen in Fig. 1. At a low... 

The polymer complex takes a very compact form and metal ions are crowded within the contracted polymer chain (Scheme 2), so that an interaction between the metal ions is expected in the catalysis of heteronuclear polymer complex. 

Later, Tieke reported the UV- and y-irradiation polymerization of butadiene derivatives crystallized in perovskite-type layer structures [21,22]. He reported the solid-state polymerization of butadienes containing aminomethyl groups as pendant substituents that form layered perovskite halide salts to yield erythro-diisotactic 1,4-trans polymers. Interestingly, Tieke and his coworker determined the crystal structure of the polymerized compounds of some derivatives by X-ray diffraction [23,24]. From comparative X-ray studies of monomeric and polymeric crystals, a contraction of the lattice constant parallel to the polymer chain direction by approximately 8% is evident. Both the carboxylic acid and aminomethyl substituent groups are in an isotactic arrangement, resulting in diisotactic polymer chains. He also referred to the y-radiation polymerization of molecular crystals of the sorbic acid derivatives with a long alkyl chain as the N-substituent [25]. More recently, Schlitter and Beck reported the solid-state polymerization of lithium sorbate [26]. However, the details of topochemical polymerization of 1,3-diene monomers were not revealed until very recently. 

Flory has defined the theta temperature as that temperature at which the pointer exists in a advent in an unperturbed conformation. The polymer chain ft[pt nh as the temperature is increased and contracts m the temperature to decreased below the theta temperature. 

The higher reactivity of the PVMI-Co(III) complex is attributed to the electrostatic domain of the polymer complex, as in the above PVP system. When the PVMI chain contracts, the charge density in the polymer domain increases and the reaction rate also increases. On the other hand, when the polymer chain expands, the electrostatic domain is weakened, which produces a fall in reactivity. These results confirm that the conformation of the polymer complex is closely related to the strength of its electrostatic domain and to the reaction rate. The effects of the polymer chain on reactivity are to be understood not only in terms of static chemical environment but also as dynamic effects which vary with the solution conditions, e.g. pH, ionic strength, solvent composition, temperature, and so on. 

The expansion and contraction of the polymer chain which accompanies the redox of Cu ions can also be visually confirmed by means of the mechanochemical system proposed by Kuhn161), as illustrated in Fig. 31. A film is prepared with a poly(vinylalcohol)-Cu(II) complex and is suspended with a sinker in water. The film is extended by about 20% on the reduction of Cu(II) to Cu(I) and shrinks back to its original length on the oxidation of Cu(I). The poly(vinylalcohol) chain is densely crosslinked by the extremely stable Cu(II) chelate, but is loosened when Cu ion forms the unstable Cu(I) chelate. This change is reversible as may be observed. 

In the catalyst reoxidation step, contrary to the electron-transfer step, the polymer ligand should shrink because of the formation of the Cu(II) complex. Therefore, the polymer chain may partially repeat are expansion and contraction occurring during the catalytic cycle. When one has a view of the polymer-Cu catalyst as a whole, each part of the polymer catalyst domain, which is drifted in solution, is seen to be fluctuating during the catalytic process [Fig. 32(b)]. The fluctuating shape of biopolymers in enzymic reactions has been pointed out, and the dynamically conformational change of a flexible polymer chain is considered to be one of the effects of the polymer catalyst. 

Control of the electron-transfer step was also attempted by combining two metal species on a polymer ligand167. We prepared polymer-metal complexes involving both the Cu(II) and Mn(III) ions. The oxidative polymerization of XOH catalyzed by the PVP-Cu, Mn mixed complex or the diethylaminomethylated poly(styrene)(PDA)-Cu Mn mixed complex proceeded 10 times faster than the polymerization catalyzed by either PVP- or PDA-metal complex. The maxima of the activity observed at [Cu]/[Mn] = 1 and [polymer]/[Cu,Mn] moderately small where Cu and Mn ions were crowded within the contracted polymer chain. Cooperative interaction between Cu and Mn was inferred. The rate constant of the electron-transfer step (ke in Scheme 14) for Cu(II) -> Cu(I) was much larger than that for Mn(III) -> Mn(II). The rate constants of the reoxidation step (k0) were polymer-Mn ex polymer-Cu.Mn > polymer-Cu, so the rapid redox reaction... 

Let us first consider a network immersed in a melt of polymer chains with degree of polymerization p. In the athermal case, the network should be swollen. As polymer-network interaction parameter Xnp increases, the volume of the network decreases until a practically complete segregation of the gel from polymer melt occurs. It has been found [34, 35] that two qualitatively different regimes can be realized either a smooth contraction of the network (Fig. 8, curve 1) or a jumpwise transition (Fig. 8, curve 2). The discrete first order phase transition takes place only for the networks prepared in the presence of some diluent and when p is larger than a critical value pcr m1/2. The jump of the... 

It implied that the motion of P P is suppressed by the microviscosity created by hydrophobic contracted polymer chain aggregation. On the other hand, the ryjda jj of PQ3P dissolved in PIPAAm-b-PBMA micelle solutions were markedly lowerthan those of PIPAAm solutions overthe entire temperature region owing to highly compact cores of aggregated PBMA chains. 

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