The formation of gradient interfaces between PS-and PB-rich microphases in SBS block copolymers was investigated by means of solid-state NMR and solution NMR as well as TEM, AFM, and SAXS as a function of molecular architecture, comparing linear and star-shaped asymmetric block structures, and gradient as well as random incorporation of styrene comonomer into the PB-rich blocks. Although all studied SBS possess a very similar total styrene content, different morphologies and mechanical properties were found in the extruded SBS/PS blends, whose origin could be related to the formation of a compositional interface gradient. Employing the sensitivity of solid-state NMR for hard (glassy) and soft (rubbery) phases as well as their respective chemical compositions, we found that upon raising the temperature up to the PS glass transition different amounts of polystyrene from the hard PS phase "soften" and integrate into the soft PB-rich phase ("PS softening"). The degree of "PS softening" characterizes the interfacial gradients of SBS block copolymers at elevated temperatures up to the melt. The softened PS was found to partially mix into the soft phase and partially remain at the interface, thus forming different gradient interfaces, depending primarily on the amount of styrene randomly incorporated in the PB mobile blocks and much less on a compositional gradient at the block linkages in SBS chains. In SBS/PS blends, SBS with a substantial "PS softening" effect was found to preferentially form elongated PB lamellar morphologies, which lead to improved mechanical ductility. The purpose of this study was to apply different characterization methods and correlate their results in order to gain important compositional and morphological information as well as their effects on the SBS/PS blend mechanical properties. Rapid and robust low-cost pulsed solid-state NMR methods were established as versatile analytical tools for application in high-output polymer screening (HOPS) and quality control systems, enabling online monitoring of structure-property correlations as well as product quality of SBS-based materials.

We demonstrate the fast, direct, and quantitative observation of temperature-and comonomerinduced changes in the interfacial size and composition in phase-separated styrene-butadiene-styrene block copolymers by double-quantum-filtered proton spin-diffusion NMR experiments performed under high-resolution magic-angle spinning conditions. The experiment is based on the dipolar-mediated diffusion of spin magnetization from the (styrenic) rigid phase through a more mobile interphase of variable size and composition into the soft (polybutadiene) domain. The experiment spectroscopically distinguishes between mobilized styrene segments located in the interphase and those mixed (dissolved) in the bulk of the mobile domain. The results indicate that temperature-induced softening due to mobilization of styrene units at the interface and the tendency to become part of an extended interphase is stronger for systems with a lower segregation strength, having statistically distributed styrene comonomers in the soft domain.

Poly(p-xylylene) (PPX) and its derivatives were prepared by vapor-phase pyrolysis and subsequent chemical vapor deposition (CVD) of the pyrolysis products. Readily available esters of R,R′-dihydroxy-p-xylylenes were utilized as starting materials. Mechanistical studies prove that 1,4-quinodimethane is formed by pyrolysis of diesters. The PPXs obtained compare well to PPXs obtained by the classical route using [2.2]paracyclophanes. 13 C CP-MAS NMR spectroscopy indicates that the arrangement of substituents along the polymer main chain is controlled by the size of substituents.

Poly(p‐xylylene) (PPX) was prepared by vapor phase pyrolysis of [2.2]paracyclophane following the procedure of Gorham. PPX was obtained in different crystalline modifications by dry annealing, dissolution and reprecipitation under different conditions. These samples were analyzed by WAXS and 13C CP‐MAS NMR spectroscopy. Clear evidence was found that the presence of different crystalline modifications is responsible for the unexpected 13C CP‐MAS NMR spectrum as observed for as‐polymerized PPX. An attempt was made to explain the differences observed in the 13C CP‐MAS NMR spectra of different crystalline modifications by different chemical environments utilizing simulations of the crystal unit cells.

In a previous deuterium NMR study conducted on a liquid crystalline (LC) polymer with laterally attached book-shaped molecules as the mesogenic moiety, we have revealed a biaxial nematic phase below the conventional uniaxial nematic phase (Phys. Rev. Lett. 2004, 92, 125501). To elucidate details of its formation, we here report on deuterium NMR experiments that have been conducted on different types of LC side-chain polymers as well as on mixtures with low-molar-mass mesogens. Different parameters that affect the formation of a biaxial nematic phase, such as the geometry of the attachment, the spacer length between the polymer backbone and the mesogenic unit, as well as the polymer dynamics, were investigated. Surprisingly, also polymers with terminally attached mesogens (end-on polymers) are capable of forming biaxial nematic phases if the flexible spacer is short and thus retains a coupling between the polymer backbone and the LC phase. Furthermore, the most important parameter for the formation of a biaxial nematic phase is the dynamics of the polymer backbone, as the addition of a small percentage of low molar mass LC to the biaxial nematic polymer from the original study served to shift both the glass transition and the appearance of detectable biaxiality in a very similar fashion. Plotting different parameters for the investigated systems as a function of T/Tg also reveals the crucial role of the dynamics of the polymer backbone and hence the glass transition.

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* P e r m a n e n t address: University of M O S U~, Iraq SUMMARY Conformations of macromolecules have been determined in semicrys t a l l i n e as well as i n glassy phase by variable t e m p e r a t u r e 13C and 29%-NMR Magic Angle Spinning (MAS). Assignment of t h e conform e r s has been achieved with t h e aid of low molecular weight representative models, f r o m slow exchange solution s p e c t r a as well as f r o m solid state MAS d a t a . The dominant influence of y -e f f e c t s on t h e chemical shift is discussed. Conformational analysis has been performed on poly(ethylene), on d i t a c t i c h e a d -t ohead poly(propy1ene)s and poly(vinylchloride)s, on poly(dimethylsi1ox-ane) and on t h e respective low molecular weight models. INTRODUCTIONHigh resolution solid state NMR with roton enhancement (PE)