Microphase kinetics

Fraaije, J.G.E.M. Dynamic density functional theory for microphase separation kinetics of block copolymer melts. J. Chem. Phys. 99 (1993) 9202-9212. 

Methyl-l,10-undecadiene, ADMET polymerization of, 442 Michaelis-Menten enzymatic kinetics, 84 Microbial hydrolysis, 43 Microcellular elastomers, 204-205 Microphase-separated block copolymers, 6-7... 

The ITIES with an adsorbed monolayer of surfactant has been studied as a model system of the interface between microphases in a bicontinuous microemulsion [39]. This latter system has important applications in electrochemical synthesis and catalysis [88-92]. Quantitative measurements of the kinetics of electrochemical processes in microemulsions are difficult to perform directly, due to uncertainties in the area over which the organic and aqueous reactants contact. The SECM feedback mode allowed the rate of catalytic reduction of tra 5-l,2-dibromocyclohexane in benzonitrile by the Co(I) form of vitamin B12, generated electrochemically in an aqueous phase to be measured as a function of interfacial potential drop and adsorbed surfactants [39]. It was found that the reaction at the ITIES could not be interpreted as a simple second-order process. In the absence of surfactant at the ITIES the overall rate of the interfacial reaction was virtually independent of the potential drop across the interface and a similar rate constant was obtained when a cationic surfactant (didodecyldimethylammonium bromide) was adsorbed at the ITIES. In contrast a threefold decrease in the rate constant was observed when an anionic surfactant (dihexadecyl phosphate) was used. 

The fascinating thermodynamics of block copolymers that results from microphase separation are the subject of the parts 2.2,2.3, and 2.4 of Chapter 2. Part 2.4 is concerned with the complex kinetic processes that accompany phase transitions, and the dynamic processes controlled by the structure of the block copolymer melt. 

Figure 18c displays swelling kinetics of two SV films with the same initial thickness but different microphase-separated structures. The curves show up to 10% larger swelling (smaller poi) of SV films with the initial bulk lamella morphology as compared to the films with the non-bulk micelle phase [119],... 

Dwight D, McGrath JE, Lawson G, Patel N,York G (1989) Surface and bulk microphase separation in siloxane-containing block copolymers and their blends The roles of composition and kinetics from multiphase macromolecular systems. BM Culbertson (ed) Plenum, pp 265-288... 

A rougher but useful estimate of the unique activities may be made by assuming that each lies half-way along the cadmium activity overlap observed between two microphases. Since the transformations appear to become more probable with greater defect concentrations, the estimates have some kinetic basis. 

Quantitative approaches to describing reactions in micelles differ markedly from treatments of reactions in homogeneous solution primarily because discrete statistical distributions of reactants among the micelles must be used in place of conventional concentrations [74], Further, the kinetic approach for bimolecular reactions will depend on how the reactants partition between micelles and bulk solution, and where they are located within the microphase region. Distinct microphase environments have been sensed by NMR spectrometry for hydrophobic molecules such as pyrene, cyclohexane and isopropylbenzene, which are thought to lie within a hydrophobic core , and less hydrophobic molecules such as nitrobenzene and N,N-dimethylaniline, which are preferentially located at the micelle-water interface [75]. Despite these complexities, relatively simple kinetic equations for electron-transfer reactions can be derived for cases where both donors and acceptors are uniformly distributed inside the micelle or on its surface. 

MSI) that uses the same time-dependent Ginzburg Landau kinetic equation as CDS, but starts from (arbitrary) bead models for polymer chains. The methods have been summarized elsewhere. Examples of recent applications include LB simulations of viscoelastic effects in complex fluids under oscillatory shear,DPD simulations of microphase separation in block copoly-mers ° and mesophase formation in amphiphiles, and cell dynamics simulations applied to block copolymers under shear. - DPD is able to reproduce many features of analytical mean field theory but in addition it is possible to study effects such as hydrodynamic interactions. The use of cell dynamics simulations to model non-linear rheology (especially the effect of large amplitude oscillatory shear) in block copolymer miscrostructures is currently being investigated. ... 

Erosion kinetics is complicated when the anhydride monomers of a copolymer system exhibit microphase separation that leads to the erosion of different phases... 

A recent SECM study of electrochemical catalysis at the ITIES was based on a similar concept (23). The ITIES was used as a model system to study catalytic electrochemical reactions in microemulsions. Microemulsions, i.e., microheterogeneous mixtures of oil, water, and surfactant, appear attractive for electrochemical synthesis and other applications (63). The ITIES with a monolayer of adsorbed surfactant is of the same nature as the boundary between microphases in a microemulsion. The latter interface is not, however, directly accessible to electrochemical measurements. While interfacial area in a microemulsion can be uncertain, the ITIES is well defined. A better control of the ITIES was achieved by using the SECM to study kinetics of electrochemical catalytic reduction of //zms-l, 2-dibromo-cyclohexane (DBCH) by Co(I)L (the Co(I) form of vitamin B12) ... 

Sofia P, Fiilber C, Demco DE, Bliimlich B, Spiess FTW (1996) Effect of residual dipolar interactions on the NMR relaxation in cross-linked elastomers. Macromolecules 29 6222-6230 Suzuki M, Hirasa O (1993) An approach to artificial muscle using polymer gels formed by microphase separation. Adv Polym Sci 110 241-261 Tanaka T, Fillmore DJ (1979) Kinetics of swelling of gels. J Chem Phys 70 1214—1218 Tanaka T, Hooker LO, Benedek GB (1973) Spectrum of light scattered from a viscoelastic gel. J Chem Phys 59 5151-5159... 

Some phase diagrams of low-polydispersity amphiphilic block copolymers, exhibit areas of coexistence over a relatively wide range of composition (see Fig. 4) [32]. This is probably due to kinetic inertia or to the fact that at the borderline between two thermodynamically stable phases the energetic differences between two structures are marginal. Swelling these coexisting phases with a siliceous precursor affords a microphase-separated siliceous phase, which has the same structure as the binary mixture consisting of water and amphiphilic... 

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