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Dynamic light scattering measurements on a symmetric polystyrene-polyisoprene diblock copolymer, Mw = 3.4 x 106, dissolved in neutral good solvents are reported. The solvents comprise mixtures of toluene and -chloronaphthalene, and the solvent compositions necessary to index-match the entire copolymer, the polystyrene block, and the polyisoprene block have been determined. The first of these, the zero average contrast (ZAC) condition, is particularly advantageous as it eliminates the cooperative diffusion mode, thus enhancing the relative amplitude of the elusive internal mode. However, the ZAC condition is sensitive to small changes in either solvent composition or temperature. In dilute and semidilute ZAC solutions, the correlation functions consistently show two modes. The slower mode is diffusive, with a diffusivity in close agreement with that measured by pulsed-field-gradient NMR; it is thus interpreted as the heterogeneity mode, which is visible due to chain-to-chain variations in composition.The faster mode is the internal mode, with a decay rate that is independent of scattering angle and decreasing with concentration; the concentration dependence is that observed for the viscoelastic longest relaxation time. For polymer concentrations within a factor of 2 of the order-disorder transition, the total scattered intensity increases markedly, which is attributed to the appearance of large-amplitude concentration fluctuations. It is also shown that in dilute solution, the heterogeneity and cooperative modes have comparable decay rates, which can complicate the interpretation of the diffusional second virial coefficient, k¿, for copolymers.

Low dielectric constant polymers offer many advantages in circuit performance, such as power dissipation, crosstalk and RC delay, when used as inter-layer dielectrics (ILDs). Silicon dioxide, a material commonly used as an ILD has a dielectric constant of 4.0. Organic polymers that have dielectric constant values ranging from 2.0 to 3.0 offer attractive alternatives to SiO2. However, it has been a great challenge to find organic polymers with thermal stability up to 450 °C. We have characterized thermal properties of polymers using thermal desorption analysis. isothermal TGA and FTIR to identify weak functional groups. In addition, we have measured the hardnesses and moduli of these polymers and found that the values are much lower than those of SiO2.Stress distributions in the interconnect system were analyzed using finite element modeling in order to understand potential reliability problems.

The sizes and shapes of star‐shaped poly(vinyl ether)s, prepared by living cationic polymerization, were studied by dynamic light scattering and molecular mechanics‐based computer simulation. The hydrodynamic radii (Rh) of star poly(isobutyl vinyl ether)s (4a; M̄w = 2.2 × 104 − 1.7 × 105) determined by dynamic light scattering were in the range from 30 to 90 Å in tetrahydrofuran or ethyl acetate. Consistent with the expected multiarmed architecture of 4a, the radius for a given number (f) of arms per molecule increased with the degree of polymerization [DP(arm)] of the arms, and for a fixed DP(arm), the radius increased with f. The relationship between arm number f and the “shrinking” factor h [Rh(star)/Rh(linear)] was consistent with multibranched structures for the star polymers. These results are supported by those for the molecular weight itself; the apparent weight‐average molecular weights by size‐exclusion chromatography are less than the corresponding absolute values by static light scattering. The dependence of h on f suggests some degree of asymmetry in the star shape. Similar results were also obtained by the computer simulation of potential energy‐minimized conformations of the arms, which implied almost spherical but slightly asymmetric shapes. The computer simulation also demonstrated that the star polymer (4b) with pendant hydroxyl groups in the arms is smaller in size than the corresponding alkyl (isobutyl) (4a) with the identical arm number and arm degree of polymerization. © 1995 John Wiley & Sons, Inc.