Copolymer systems, measurement

The fraction of sequences of the length indicated below have been measured t for a copolymer system at different feed ratios ... 

Reactivity ratios for 1-hexene (M ) with 5-methyl-1,4-hexadiene CM2) copolymerization at 30 c in hexane solvent using a Et2AlCl/6-TiCl3 AA catalyst system (Al/Ti atomic ratio s 1.5) were determined. The compositions of copolymers were measured by 300 MHz 1H-NMR spectroscopy. The reactivity ratios, calculated by the Tidwell-Mortimer method, were 1.1 + 0.2 for each of the two monomers. 

The etch rate measurements for positive and negative-behaving e-beam resists are found in Table V. It is apparent that the etch resistance is lower the more sensitive the positive resist. The exception would be PMCN, which exhibits better dry-etch resistance than that which would be predicted based on e-beam sensitivity alone. Where e-beam sensitivity and etch resistance are needed, copolymerization becomes very important. This has been demonstrated for the MCN/MMA and MCA/MCN model copolymer systems in references 9 and 10, respectively. 

Campbell (22) refers that copolymers of 4-methyl- 1-pentene (4MP) with M-pentene-1 and with w-hexene-1, synthesized with the aid of stereospecific catalysts, were crystalline for M-hexene contents up to 25%, probably because of a partial cocrystallization. Analogous conclusions were attained by Hewett and Weir (23) for the same copolymer systems studied by Campbell on the basis of dynamic measurements correlated with DTA observations. 

Conformations of the polymers were studied by CD and optical rotation measurements. Poly-L-lysine is known to exist in disordered, helical and -conformation, depending on the temperature, pH of the system and the solvent used. The side chain of the polymer has a significant effect on the backbone conformation. At neutral pH, poly-L-lysine exists in a random coil structure while at pH above 10, the e-amino group becomes a neutral form and the polymer undergoes transition to a helical structure. In order to elucidate the effect of base substituents on the conformation of poly-L-lysine, CD spectra of the copolymer were measured. 

Oxygen barrier data for pure H40 systems and H40 network systems measured at RT and 0 and 50%RH are summarized in Table 1 which also reports Tg s and densities in the dry state. Due to the high concentration of hydroxyl functional groups in the periphery, excellent gas barrier characteristics for pure H40 are predicted. As seen in Table 1, the pure H40 at 0%RH displayed considerably better oxygen barrier characteristics than PET and comparable to those for EVOH with 48% (mol/mol) of ethylene. EVOH copolymers with low and moderate ethylene content are considered benchmark materials for packaging applications. When exposed to ambient humidity (50% RH) the barrier properties were reduced, but still better than PET. Figure 6 (a), (b), and... 

The application of dual detection [UV and refractive index (RI)] to the SEC analysis of polystyrene-poly(methyl methacrylate) (PS-PMMA) has already been studied in this laboratory (2). Both MWD and CCD were determined using a methodology outlined by Runyon et al. (3). This approach relies on SEC column calibration with narrow polydis-persity standards for each of the homopolymers as well as a measure of the detector response factors for each homopolymer to produce a copolymer MWD. In the case of PS and PMMA this is feasible, but in other block copolymer systems the availability of suitable molecular weight standards may be more limited. In addition, this procedure does rely on true SEC and is not valid for block copolymers for which the universal calibration does not hold true for both blocks in a given solvent system. 

In the Current State of the Art we will review some of the recent SANS and reflectivity data from ISIS, which also serve to point to future directions and opportunities. Recent reflectivity measurements, on the adsorption of polymers and polymer/surfactant mixtures at interfaces, surface ordering in block copolymer systems, time dependent inter-diffusion at polymer-polymer interfaces, and the contribution of capillary waves to interfacial widths, will be described. The use of SANS to investigate the dynamic of trans-esterification of polyester blends, the deformation of copolymers with novel morphologies, and the use of diffraction techniques to determine the structure of polymeric electrolytes, will be presented. 

Advances in our understanding of thermodiffusion in polymer solutions have led to the application of ther-mal FFF to copolymers. With random copolymers, for example, the dependence of on chemical composition is now predictable [6], so that compositional information can be obtained from retention measurements. With block copolymers, thermal FFF can still be used to separate components according to molecular weight, branching, and composition, but independent measurements on the separated fractions must be made in order to get quantitative information, except when special solvents are used. Special solvents yield a predictable dependence of Dj on composition even for block copolymers [6]. Different solvents are special for different copolymer systems. 

Polystyrene and polybutadiene homopolymers as well as random and block copolymers of these mers have been studied via dielectric relaxation spectroscopy and tensile stress-strain measurements. The results suggest that some block copolymer systems studied have styrene rich surfaces which appear to partially crosslink upon initial exposure to ozone even though surface oxygen concentrations are not significantly affected. After continued exposure these samples appear to then undergo chain scission. Complex plane analysis implies that after degradation... 

Segmental motions of P(3HB) and P(3HB-co-27%3HV) in chloroform-d solution have been studied by measuring NMR relaxation times and NOE factors as a function of temperature [72, 73]. Analysis of the relaxation data on the basis of the Dejean-Laupretre-Monnerie (DLM) model, which describes the dynamics of polymer chains [74], indicates that the local dynamics of a comonomer unit, e.g., 3HB, are independent of the presence of a nearby 3HV unit and vice versa that segmental motion of the P(3HB-co-27%3HV) copolymer described by cooperative conformational transitions [73] is similar to that for the P(3HB) homopolymer [72]. These motional characteristics of the P(3HB-co-3HV) copolymer chain are consistent with the conformational characteristics derived by the analysis of spin coupling as shown in Section 21.2.2.3 [63] and are consistent with the occurence of cocrystallization in this copolymer system. 

Viscosities of the copolymers were measured in Freon 113 at 35 °C (Figure 9). For copolymers of hexafluoroacetone and ethylene, the intrinsic viscosity is much higher at -78°C than at 0°C. A similar trend has been observed for the ternary system of ethylene-tetrafluoro-ethylene-hexafluoroacetone (7). 

Statistical copolymers of uBA and IBA with different molecular weights and compositions were synthesized under ATRP conditions, as described in detail earlier (26). In all ATRP reactions, a CuBr/PMDETA complex was used since it is commercially available and well mediates controlled polymerization of acrylate monomers. Polymerizations were performed at 50°C in acetone/anisole mixture using EtBrIB as the initiator. The schematic representation of all prepared materials is shown in Scheme 2. The solid line represents a series of polymers with similar DP but systematically increasing IBA content. Another such group of copolymers is indicated with a dashed line. Copolymers with similar IBA/nBA ratio but different degree of polymerization (DP), i.e., the dotted line, were also synthesized. When comparing the thermo-mechanical properties of acrylate homopolymers and P(IBA-co-nBA) copolymers, the first important question is whether the copolymer system is isotropic in the bulk state or rather exhibits a micro-phase separation. To answer this question, the DSC thermograms for all samples shown in Scheme 2 were measured. 

One method used to evaluate the upper working temperature of block copolymer systems is to measure the shear adhesion failure temperature (SAFT), a useful method to discover exactly what has been gained in the upper working temperature limits when resins are added to the styrene domain of polystyrene end-block systems to increase the effective glass transition temperature. Typically the test is set up as a standard shear test, either to the standard stainless steel panel or to polyester, with a 1 in. by 1 in. (25 mm by 25 mm) area and a load of 1 kg. The set-up is placed in an oven that can be accurately controlled so that the temperature is increased by 2.0°C (3.6°F) per minute, the temperature at which failure occurs being recorded as the SAFT. 

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