A series of symmetric and asymmetric poly(di-ra-alkylsilanes) have been investigated to assess their minimum-energy conformations, crystal packing, and, in the case of poly(di-n-tetradecylsilane) (PdnTDS), the conformation of the n-alkyl side chains. All of the polymers exhibit a thermochromic transition. X-ray diffraction measurements were made above and below the transition temperature to determine unit ceil parameters for both the ordered and disordered phases. A TGTG' silicon backbone conformation has been identified and found to occur routinely in symmetric poly (di-n-alkylsilanes) having side chain lengths between 9 and 14 carbon atoms. This unique conformation has previously been shown to be energetically feasible by molecular modeling calculations. Spectroscopic measurements on PdnTDS indicate that the side chains have predominantly an all-trans conformation. In all the polysilanes studied above their transition temperatures, it has been found that the backbone conformations become somewhat disordered, but the chains maintain a columnar arrangement on a hexagonal lattice. X-ray diffraction patterns from the disordered phases feature one strong and one or two weaker equatorial reflections. The d-spacing of the strongest reflection, which relates directly to the radius of the cylindrical molecular envelope, increases as the lengths of the n-alkyl side chains increase, apparently to accommodate the extra side chain length. The side chains themselves are disordered above the transition. Based on molecular models and the X-ray values of the cylindrical radii, the side chains are not extended but on average are shortened, presumably by the presence of one or more gauche bonds.

Oxygen quenching of pyrene has been studied in a diverse series of polymers. Most measurements were made using homo- or copolymers containing a poly(dimethylsiloxane) region. Systematic variations in the polymer properties have been made in order to delineate the structural features important for satisfactory use as supports for oxygen sensors. In particular, quenching behavior was examined as a function of the type and amount of copolymer cross-linkers; these were added to produce domains of different polarity and rigidity that would segregate the sensor molecule. A domain model (Xu, W.; et al. Anal. Chem. 1994, 66, 4133-4141) was used to explain the variations in oxygen-quenching properties as a function of additives and cross-linkers. The relative affinity of the different domains for the pyrene and the efficacy of the domains for oxygen quenching controls the overall behavior of the sensing response.

Two series of macromolecular complexes of poly(ethylene oxide) (PEO) [100K and 600K]/sodium poly(α,l-glutamate) (PGNA) [MW 1K and 45K] and poly(ethylene glycol) [MW 350−2000]/PGNA [1K] have been prepared by solution blending using water/methanol mixtures. All the macromolecular complexes were soluble in water. The PGNA/PEO macromolecular complexes were mechanically reliable opaque films and may be stretched a couple of fold to form white opaque fibrils. Formation of the α-helical conformation of PGNA in the complexes was determined by CD studies; e.g., the CD spectrum of a film of PGNA 1K−PEO 600K (1:2.5, w/w) complex showed a positive peak at 200 nm and two negative peaks at 207 and 220 nm, indicating the presence of the α-helical PGNA conformation in the complex. FT-IR spectra of the complexes support the presence of the α-helical PGNA conformation in the macromolecular complexes. Wide-angle X-ray diffraction (WAXD) patterns of the PGNA 1K−PEO 600K (1:2.5 and 1:5, w/w) indicate that some of the PEO crystalline segments in the complex form a near planar zigzag conformation. Solution 23Na and 2D-NOESY 1H NMR spectra of the complexes in nonaqueous solvents revealed interaction between the PEO and PGNA at the following sites:  CH2−CH2 (of PEO) and γ-CH2− (of PGNA) [hydrophobic interaction] and 〉O- - -Na+ [ion−dipole interaction]. In aqueous solutions, ion−dipole complex sites dissociated completely to form free (solvated) sodium ions, and the number of contact points interacting through hydrophobic interactions was reduced significantly and diminished in dilute solutions. The proposed solid-state structure of the macromolecular complex is a helical PGNA core; PEO crystalline segments having near planar zigzag conformations; glutamate and ethylene oxide segments interacting through ion−dipole interaction; and β and γ groups of PGNA side groups interacting with PEO segments through hydrophobic interactions.

Poly(di-n-pentylsilane) has been previously reported to adopt a 7/3 helical conformation at room temperature. We have studied the solid state structure of a low molecular weight (Mv = 46 000) sample and its dependence on temperature using wide angle X-ray diffraction, differential scanning calorimetry, and Raman spectroscopy. The results suggest that domains of two distinct structures are present, one having an all-trans conformation and the other a 7/3 helical conformation. The all-trans conformation was observed (even at room temperature) in samples cooled previously to -15 °C. Characteristic resonance enhancement of certain Raman vibrations is observed for the planar zigzag polymorph. The all-trans material converts to the 7/3 helical structure at 35 °C and subsequently undergoes an order/disorder transformation at about 56 °C.

C-477 stmctures obtained are essentially the same as Bunn's model. The molecule slightly rotates as the temperature increases. The discrepancy factors are not so good. This may be attributed to the fact that the hydrogen atoms associated with hydrogen bonds were ignored. Therefore, the difference synthesis was made by using the data at lOOK. It is possible to find three peaks on the map of the difference synthesis. Two peakes can be interpreted by the intennolecular hydrogen bonds as Bunn suggested. Third peal' should be attlibuted to the intramolecular hydrogen bonds in the isotactic sequence of the atactic configuration, which was first proposed by Murahashi et al. for the isotactic poly(vinyl alcohol).