Crystallizable polymers often form multiple stacks of uniquely oriented lamellae, which have good registry despite being separated by amorphous fold surfaces. These correlations require multiple synchronized, yet unidentified, nucleation events. Here, we demonstrate that in thin films of isotactic polystyrene, the probability of generating correlated lamellae is controlled by the branched morphology of a single primary lamella. The nucleation density n(s) of secondary lamellae is found to be dependent on the width w of the branches of the primary lamella such that n(s) ∼ w(-2). This relation is independent of molecular weight, crystallization temperature, and film thickness. We propose a nucleation mechanism based on the insertion of polymers into a branched primary lamellar crystal.

New crystalline nanostructured inorganic–organic hybrid materials containing isotactic polystyrene (iPS) are prepared by means of hydrosilylation coupling of vinyl‐terminated iPS with octakis(dimethylsilyloxy)silsesquioxane (Q8M8H). The number average molar mass of the iPS chains varies between 2000 and 6000 g mol−1. As a function of the iPS/Q8M8H ratio, using excess reagent, the formation of linear or star‐shaped hybrid architectures is achieved. Via fractionation, it is possible to isolate well‐defined linear hybrids containing one iPS chain and seven ethyl groups per silica core (iPS‐Q8M8E7) as well as star‐shaped hybrids containing up to eight iPS side chains (iPS6‐8‐Q8M8). These new iPS/polyhedral oligomeric silsesquioxane hybrid materials crystallize when the number average molar mass of iPS side chain exceeds 5500 g mol−1. The hydrosilylation coupling reaction and the resulting linear iPS‐Q8M8E7 and star‐shaped iPS6‐8‐Q8M8 are characterized by NMR spectroscopy, size exclusion chromatography (gel permeation chromatography), and polarized light microscopy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

In semicrystalline polymers, the segments around the crystallites typically relax significantly slower than in the purely amorphous phase. This results in an, on average, slower dynamics. Here we present a contrary effect in a star-shaped polymer based on a polyhedral oligomeric silesquioxane (POSS) molecule as center and isotactic polystyrene arms. Measurements by means of broadband dielectric spectroscopy reveal a reduction of the mean relaxation time by up to 1 decade. Analyzing the relaxation time distribution unravels three moieties of different dynamics beyond the crystalline fraction. These are assumed to form respective domains: a rigid amorphous fraction around crystallites, a mobile amorphous fraction, and a confined amorphous fraction of enhanced dynamics presumably located around the POSS centers. Probably, the crystallites in combination with the starlike architecture stabilize the average volume which balances the higher density of the growing crystallites by an increase in free volume in the amorphous domains.

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Reactor blend formation of soluble highly isotactic polystyrene (iPS) enables tailoring of bimodal iPS molar mass distributions containing variable amounts of ultrahigh molar mass iPS (UHMWiPS). A key feature is the facile iPS molar mass control, achieved by homogeneous catalytic styrene polymerization on a MAO-activated titanium bisphenolate catalyst, using 1,9-decadiene as chain transfer agent. Whereas UHMWiPS (M w of 947 000 g mol–1) is formed in the absence of the diene, the molar mass M w increases from 191 000 to 482 000 g mol–1 with decreasing diene/styrene molar ratio. In a cascade of two parallel reactors, polymerizing styrene in the presence and the absence of diene, the mixing ratio of the resulting two iPS solutions governs the UHMWiPS content of the reactor blends (RB-2). Hence, the contents of iPS and UHMWiPS are varied without affecting the average molar mass of both blend components. In reactor blends (RB-1), produced in a single reactor with delayed diene injection, molar mass and polydispersity of iPS/UHMWiPS as well as molar mass of the iPS fraction and UHMWiPS depend on the diene/styrene molar ratio and the delay time of the diene injection. In this study, we investigate the influence of both iPS molar mass and iPS molar mass distributions on crystallization behavior and viscoelastic properties. The correlation of zero shear viscosity with the iPS molar mass exhibits scaling of 3.4, typical for linear polymer chains. Below 10 wt % UHMWiPS content, bimodal iPS molar mass distribution enhances processability by shear thinning.