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Monoalkyl-and dialkyl-imidazolium surfactants were used to prepare organically modified montmorillonites with markedly improved thermal stability in comparison with their alkyl-ammonium equivalents (the decomposition temperatures increased by ca. 100°C). Such an increase in the thermal stability affords the opportunity to form syndiotactic polystyrene (s-PS)/imidazolium-montmorillonite nanocomposites even under static melt-intercalation conditions in the absence of high shear rates or solvents. Upon nanocomposite formation, s-PS exhibited an improvement in the thermal stability in comparison with neat s-PS, and the ␤-crystal form of s-PS became dominant. This crystallization response agrees with previous studies of s-PS/pyridinium-montmorillonite hybrids and is tentatively attributed to a heterogeneous nucleation action by the inorganic fillers.

This paper discusses a direct (one-pot) polymerization process to prepare isotactic polypropylene (i-PP) having a terminal functional group including Cl, OH, and NH2. The chemistry involves metallocene-mediated propylene polymerization using rac-Me2Si[2-Me-4-Ph(Ind)]2ZrCl2/MAO complex in the presence of styrene derivatives (St-f), carrying a Cl (St-Cl) or a silane-protected OH (St-OSi) or a silane-protected NH2 (St-NSi2), followed by hydrogenation. Apparently, the propylene propagating chain end engages in a facile consecutive chain transfer reaction, reacting with St-f and then hydrogen, with high catalyst reactivity under the proper St-f and hydrogen concentrations. The polymer molecular weight was inversely proportional to the molar ratio of [St-f]/[propylene] with a chain transfer constant (ktr/kp) of 1/21 for St-Cl, 1/34 for St-NSi2, and 1/48 for St-OSi, respectively. Both silane protecting groups were hydrolyzed in acidic aqueous solution during the sample workup step to obtain the desirable i-PP polymers with a terminal OH and NH 2 group (i.e., PP-t-St-OH and PP-t-St-NH2). The terminal functional group was confirmed by end group analysis and chain extension reaction. Despite the high molecular weight, the terminal functional group in PP engages a coupling reaction with polycapolactone (PCL) in solution and melt to form PP-b-PCL diblock copolymers that are very effective compatibilizers in PP/ PCL polymer blends.

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This article discusses an effective route to prepare amphiphilic diblock copolymers containing a poly(ethylene oxide) block and a polyolefin block that includes semicrystalline thermoplastics, such as polyethylene and syndiotactic polystyrene (s-PS), and elastomers, such as poly(ethylene-co-1-octene) and poly(ethylene-co-styrene) random copolymers. The broad choice of polyolefin blocks provides the amphiphilic copolymers with a wide range of thermal properties from high melting temperature ϳ270°C to low glass-transition temperature ϳϪ60°C. The chemistry involves two reaction steps, including the preparation of a borane group-terminated polyolefin by the combination of a metallocene catalyst and a borane chain-transfer agent as well as the interconversion of a borane terminal group to an anionic (OO Ϫ K ϩ) terminal group for the subsequent ring-opening polymerization of ethylene oxide. The overall reaction process resembles a transformation from the metallocene polymerization of ␣-olefins to the ring-opening polymerization of ethylene oxide. The well-defined reaction mechanisms in both steps provide the diblock copolymer with controlled molecular structure in terms of composition, molecular weight, moderate molecular weight distribution (M w /M n Ͻ 2.5), and absence of homopolymer.

The crystallization behavior of polymers in nanocomposites with inorganic fillers (montmorillonite In the case of PVA/MMT, crystallization of PVA is strongly promoted by MMT, also stabilizing a new crystal form not found in bulk PVA. For sPS and PP/o-MMT, crystallization is only moderately affected, exhibiting traces of simple heterogeneous nucleation and mostly bulk-like crystal structures, with very small traces on non-bulk crystals. For PEO, crystallization is impeded near the MMT surfaces, due to coordination of the surface cations to the PEO. In all cases smaller spherulite sizes develop when filler is added, independent of the size of the bulk polymer spherulites, whereas the crystallization temperature changes reflect the strength of the polymer/surface interactions.

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