DIPOLE-MOMENTS OF COPOLYMERS IN RELATION TO THE DISTRIBUTION OF POLAR MONOMER UNIT SEQUENCES

A method for evaluating the dipole moments of copolymers in relation to the distribution of polar unit sequences is proposed. Experimental data on the synthesis and dipole moments of styrene-p-chlorostyrene and styrene-p-methoxystyrene copolymers were used to calculate the effective dipole moment of a polar unit in a copolymer. For this purpose, we assumed the following effective moment values for the corresponding polar unit sequences along the copolymer chains: when both of the nearest neighbours are polar, mu(PP), when one of the nearest neighbours is polar and the other is non-polar, mu(PS), and when both of the nearest neighbours are non-polar, mu(SS). The relative magnitudes of mu(SS), mu(PS) and mu(PP) calculated for both copolymers reflect the influence of dipole-dipole interactions on the effective dipole moment of a polar unit in a copolymer molecule

Thermal, mechanical, and morphological characterization studies of poly(2,6-dimethyl-1,4-phenylene oxide) blends with polystyrene and brominated polystyrene

The miscibility of the binary and ternary blends of poly(2,6-dimethyl-1,4-phenylene oxide), brominated polystyrene, and polystyrene was investigated using a differential scanning calorimeter. The morphology of these blends was characterized by scanning electron microscopy. These studies revealed a close relation between the blend structure and its mechanical properties. The compatibilizing effect of poly(2,6-dimethyl-1,4-phenylene oxide) on the miscibility of the polystyrene/brominated polystyrene blends was examined. It was found that poly(2,6-dimethyl-1,4-phenylene oxide), which was miscible with polystyrene and partially miscible with brominated polystyrene, compatibilizes these two immiscible polymers if its contention exceeds 33 wt 9b. Upon the addition of poly(2,6-dimethyl-1,4-phenylene oxide) to the immiscible blends of polystyrene/brominated polystyrene, we observed a change in the morphology of the mixtures. An improvement in the mechanical properties was noticed. (C) 2000 John Wiley & Sons, Inc

Thermal characterization and morphological studies of binary and ternary polymeric blends of polycarbonate, brominated polystyrene, and poly(2,6-dimethyl-1,4-phenylene oxide)

The thermal behaviors of binary blends of polycarbonate (PC)/brominated polystyrene (PBrS) and ternary blends of PC/PBrS/poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) were investigated. The compatibilizing effect of PPO on the miscibility of the PC/PBrS blends was examined. The miscibility of binary and ternary blends was studied by using differential scanning calorimeter (DSC). The results of DSC indicate that the binary blends of PC/PBrS are immiscible but ternary blends of PC/PBrS/PPO in certain limits are miscible. The microstructural properties of the blends was characterized by environmental scanning electron microscope (ESEM) where the properties are determined in the natural state of the structural role of individual phases (PC/PBrS/PPO) and their effect on the overall microstructure of the products. DSC and ESEM results were supported by FT-IR measurements

New polyimide film for VLSI and its electrical characterization

Multilevel structures consisting of alternating metal and dielectric layers are necessary to achieve interconnection in high density or VLSI (very large scale integration) circuits using either nos or bipolar technology. Polyimide is one of the excellent high temperature heat-resistant polymers in organic materials and has good planarization capability and electrical insulating properties. In this work, following the synthesis of DAPDS (4,4'-bis (3-aminophenoxy)diphenylsulfone), by nucleophilic aromatic substitution of 4,4'-dichlorodiphenyl sulfone with m-aminophenol, DAPDS/pyromellitic dianhydride based soluble and processable fully imidized polyimide was synthesized successfully by using solution imidization technique. Using this specific polyimide, a metal-polyimide-silicon MIS (metal polyimide silicon) structure was manufactured. Electrical properties of the MIS capacitance have been examined. The planarizing and patterning characteristics and electrical characteristics such as current vs. voltage, breakdown field strength, permittivity and capacitance vs. voltage for quasi-static and high frequency measurements are discussed. The results are compared with conventional dielectric films used in integrated circuit fabrication

A METHOD FOR COMPARATIVE-EVALUATION OF EIT ALGORITHMS USING A STANDARD DATA SET

The point spread function (PSF) is the most widely used tool for quantifying the spatial resolution of imaging systems. However, prerequisites for the proper use of this tool are linearity and space invariance. Because EIT is non-linear it is only possible to compare different reconstruction algorithms using a standard data set. In this study, the FEM is used to generate simulation data, which are used to investigate the non-linear behaviour of EIT, the space dependence of its PSF and its capability of resolving nearby objects. It is found that for the case of iterative backprojection (IterB), the full width half maximum (FWHM) values of single-object perturbations for central, intermediate and peripheral high-contrast objects are 27%, 18% and 14% of the imaging region diameter respectively. For the method based on singular value decomposition of the Geselowitz lead sensitivity matrix (GS-SVD), the FWHM is not space dependent and is 12% of the imaging region diameter. Conclusions obtained using single-object PSF studies must also be checked with double-object or more complex perturbations because EIT is non-linear. For example, the GS-SVD method fails to detect two widely separated objects unless the truncation level of SVD is carefully adjusted. With more truncation, however, the resolution of the method is worsened. Based on these and similar observations a set of simulation data, which is proposed for comparative evaluation of different EIT algorithms, is specified and explained in the conclusion section

ABA type block copolymers of poly(monobutyl itaconate) and poly(monocyclohexyl itaconate) with poly(dimethylsiloxane): Synthesis and characterization

Monoesters of itaconic acid (monobutyl itaconate and monocyclohexyl itaconate) were synthesized and used as monomers. Poly(monobutyl itaconate) (PMBI) and poly(monocyclohexyl itaconate) (PMCHI) were prepared by free radical polymerization of these monomers using tert-butyl hydroperoxide as initiator. Subsequently, ABA type block copolymers where the A block is PMBI or PMCHI and the B block is poly(dimethyl siloxane) (PDMS) were synthesized by free radical polymerization using a macroinitiator (diperoxycarbamate) containing PDMS units. The structural formulae of the products were confirmed by spectral analysis. The molecular weights of the products are not high. Therefore the mechanical and physical properties are rather poor. However, porous structures of copolymers are observed by means of SEM