Copolymers studies

Hvidt, S Jorgensen, EB Brown, W Schillen, K, Micellization and Gelation of Aqueous Solutions of a Triblock Copolymer Studied by Rheological Techniques and Scanning Calorimetry, Journal of Physical Chemistry 98, 12320, 1994. 

Along with spectroscopic techniques, the presence of — Sn... 0=C in the copolymers studied was confirmed by viscosimetric data 2). /Ns-The dependence of intrinsic viscosity on concentration has a non-linear character, which is probably due to the conformational changew caused by the destruction of... 

Table 1 Summary of block copolymers studied in order to control microdomain orienta-tions in thin film states ...

Table 2 Summary of block copolymers studied for template nanolithographic applica-tions...

The use of nmr, —carbon-13 nmr in particular—, has given a much deeper insight into the structure of SO2 copolymers than was possible by the older, traditional method of analytically determining monomer ratios in the polymer as a function of the monomer feed. In fact, it can be safely said that the use of nmr has conpletely revolutionized the study of copolymers. (The impact of nmr on copolymer studies is studiously ignored in all polymer textbooks, which tend to reflect the status of the field twenty years ago.)... 

The polymer samples studied here fall into three distinct categories. Data from two sample populations have been combined in the SAN copolymer study. A group of SAN materials having compositions ranging from 42 (wt)% AN to 82% AN were polymerized and characterized quite some time ago (1972), with intrinsic viscosities determined only in DMF. Very recently, a second group of SAN s with compositions from 5 (wt)% to 48% AN, as well as one sample of polystyrene (0% AN), were polymerized and characterized, with intrinsic viscosities determined in DMF, THF, and MEK. These two populations are differentiated in the Results section by the designations "old data" and "new data". The third category of samples is that of S/MA copolymers and S/MA/MM terpolymers, with intrinsic viscosities measured only in MEK. 

Laquai F, Wegner G, frn C, Bassler H, Heun S (2006) Nondispersive hole transport in carbazole- and anthracene-containing polyspirobifluorene copolymers studied by the charge-generation layer time-of-flight technique. J Appl Phys 99 033710... 

Copolymers. Studies of the radiation sensitivities of amino acid homopolymers highlight the protective effect of aromatic substituents in the amino-acid side-... 

Aldehyde Copolymer Self Developing Electron-beam Resists. The ceiling temperature for the copolymerization of aliphatic aldehydes is usually below 0°C and the copolymers are easily depolymerized into monomeric aldehydes above 150°C under vacuum. This depolymerization into monomers also occurs on electron-beam or X-ray exposure as evidenced by combined gas-liquid partition chromatography-mass spectrometry. As a result, the copolymers of aldehydes behaved as self-developing positive resists and almost complete development was accomplished without any solvent treatment. Electron-beam exposure characteristics of the aliphatic aldehyde copolymers studied here are... 

Fig. 2.37 Morphologies of PHIC-PS rod-coil block copolymers studied by Chen et al. (1996). 7bp TEM images from diblocks with different compositions.The dark regions correspond to PS, which have been preferentially stained with RuG4. (A) /,., K- = 0.42 (B) /PHIC = 0.73 (C) /pH,c = 0.89 (D) /Pmc = 0.96 (E) /PHIC = 0.98. The PHIC chain axis and lamellar normals are denoted by n and p. (F, G, H) schematic models showing the packing arrangement of the rod-coil chains. The PHIC block is represented by the white rod, and the PS block by the black ellipsoid. (F) Wavy lamellar morphology (G) zig-zag morphology (H) bilayer and interdigitated arrowhead morphologies.

PS-PEO diblocks adsorbed on glass plates. Adsorption from toluene led to preferential adsorption of PEO however, due to the very high asymmetry of the copolymers studied, and the favourable adsorption energy, PS was also adsorbed. On the approach of a second coated plate, the PS volume fraction increased near the interface, indicative of strong interlayer repulsion (Cosgrove et al. 1994). 

For the nearly symmetric copolymers studied by Hashimoto et al. (1994), the mismatch in composition was small. Thus, the approximate effective Flory-Huggins interaction parameter... 

It was shown by McClain et al. that a series of PS- -PFOA copolymers studied by SANS and SAXS form polydisperse spherical core-shell micelles, where PS forms the spherical core and PFOA forms the corona, or shell, swollen with C02 (Londono et al., 1997 McClain et al., 1996b). In most cases, the core radius was 25 A, the shell radius was 85 A, and the aggregation number was 7. With an increase in C02 density implemented by decreasing the temperature, the polydispersity increased, likely from breaking a collection of aggregates of low polydispersity into a collection of smaller aggregates of higher polydispersity. 

Figures 35 and 36 reveal that for each copolymer studied, the average aggregation number (ATagg) and average hydrodynamic radius ((%)) of polymer clusters made of collapsed and associated P(DEA-co-DMA/x) chains increase and approach corresponding constants after a certain time, indicating the for-...

Figure 42 shows the temperature dependence of the average chain density ((p>) of stable mesoglobules, where (p) is defined as Mw/ 4n R l)3N /3). For all the copolymers studied, (p) always increases with the aggregation temperature. As discussed before, intrachain folding normally results in a lower chain density than interchain penetration because the chains are not infinitely flexible. For the copolymer pair, NIPAM-co-VP/60/10 and NIPAM-... 

A Michaelis-Menten profile of the catalyzed reaction was observed for the thermosensitive copolymers studied. In enzymatic catalysis, the catalytic act is preceded by the complex formation between catalyst and substrate. Because of the complex formation, enzymatic reactions follow Michaelis-Menten-type kinetics ... 

The experimental results with either technique showed that the release of 5-FU followed zero order kinetics with all copolymers studied and that the amount of 5-FU released from the copolymers increased as the amount of EHCF increased in both the EHCF HA and the EHCF HHA copolymers. This is shown in Figure 3 for some EHCF HHA and EHCF HA copolymers in the gas dispersion tube technique. 

The EHCF copolymers studied showed zero-order release kinetics in this simplified procedure and showed identical release profiles as in our earlier study (1 ) using the more complex dialysis membrane/ stainless steel mesh basket technique. The actual 5-FU release rates increased in the co-monomer order HHA>HA>BA. Within a given set of copolymers, the release rate for 5-FU increased as the EHCF content increased. 

There is a vast body of diblock copolymer studies since block choice can be such that they resemble amphiphilic surfactants. For the sake of brevity, we will skip them. Instead, we present an interesting case of triblock copolymers of poly(ethylene oxide), PEO, and poly(propylene oxide), PPO, commonly known by one of its trade names, Pluronics [117]. They have been used as non-ionic surfactants for a variety of applications such as in emulsification and dispersion stabilization. In aqueous solutions, these copolymers form micelles, and there exists a well-defined critical micelle concentration that is experimentally accessible. Several groups have investigated colloidal suspensions of these polymers [118-122], The surface properties of the adsorbed monolayers of the copolymers have been reported with respect to their structures and static properties [123-126]. 

Djermouni, B., Ache, H.J. (1980) Effect of casting solvent on the properties of styrene-butadiene-styrene block copolymers studied by positron annihilation techniques . Macromolecules, 13,168. 

Figure 21.4 Corrected melt viscosity as a function of shear stress and temperature for the three block copolymers studied. Reproduced with permission from Legge, Holden and Schroeder, Thermoplastic Elastomers A Comprehensive Review, Hanser Verlag, Munich, 1987...

After the examination of the PS photooxidation mechanism, a comparison of the photochemical behavior of PS with that of some of its copolymers and blends is reported in this chapter. The copolymers studied include styrene-stat-acrylo-nitrile (SAN) and acrylonitrile-butadiene-styrene (ABS). The blends studied are AES (acrylonitrile-EPDM-styrene) (EPDM = ethylene-propylene-diene-monomer) and a blend of poly(vinyl methyl ether) (PVME) and PS (PVME-PS). The components of the copolymers are chemically bonded. In the case of the blends, PS and one or more polymers are mixed. The copolymers or the blends can be homogeneous (miscible components) or phase separated. The potential interactions occurring during the photodegradation of the various components may be different if they are chemically bonded or not, homogeneously dispersed or spatially separated. Another important aspect is the nature, the proportions and the behavior towards the photooxidation of the components added to PS. How will a component which is less or more photodegradable than PS influence the degradation of the copolymer or the blend We show in this chapter how the... 

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