Fangming Zhu

Polymer blends of sPS/PA6 compatibilized by sulfonated syndiotactic polystyrene

Abstract Syndiotactic polystyrene (sPS) and polyamide-6 (PA6) are immiscible and incompatible and have been recognized. In this study, sulfonated syndiotactic polystyrene (SsPS-H) is employed as compatibilizer in the blend of sPS/PA6. During melt blending, the sulfonic acid groups of the SsPS-H can interact strongly with the amine end-groups of PA6 through acid–base interaction. In addition, SsPS-H is miscible with sPS when SsPS-H content is less than 20 wt.%. Therefore, the addition of SsPS-H to sPS/PA6 blends reduces the dispersed phase size and improves the adhesion between the phases. The glass transition temperatures of the PA6 component in the compatibilized blends shift progressively towards higher temperature with the content of SsPS-H-12 increase, indicating enhanced compatibility. On the other hand, the progressive lowering of the melting point and crystallization temperatures of PA6 in the blends with increasing SsPS-H contents compared to the incompatibilized blend, provide some insight into the level of interaction between the PA6 and SsPS-H. The compatibilized blends have significantly higher impact strength than the blends without SsPS-H. The best improvement in the impact strength of the blends was achieved with the content of the SsPS-H (11.9 mol%) about 5 wt.%.

Novel monotitanocene and methylaluminoxane catalyst for syndiospecific polymerization of styrene

Syndiotactic polystyrene (sPS) was synthesized with a novel monotitanocene complex of η 5 -pentamethylcyclopentadienyltri-4-methoxyphenoxy titanium [Cp * Ti(OC 6 H 4 OCH 3 ) 3 ] activated by methylaluminoxane (MAO) in different polymerization media, including heptane, toluene, chlorobenzene, and neat styrene. In all cases bulk polymerization produced sPS with the highest activity and molecular weight. Solution polymerization produced much better activity in heptane than in the other solvents. Using a solvent with a higher dipole moment, such as chlorobenzene resulted in lower activity and syndiotacticity because of the stronger coordination of solvent with the Ti(III) active species, which controlled syndiospecific polymerization of styrene. With bulk polymerization at a higher polymerization temperature the Cp*Ti(OC 6 H 4 OCH 3 ) 3 -MAO catalyst produced sPS with high catalytic activity and molecular weight. The external addition of triisobutylaluminum (TIBA) to the Cp * Ti(OC 6 H 4 OCH 3 ) 3 -MAO system catalyzing styrene polymerization led to significant improvement of activity at a lower Al:Ti molar ratio, while the syndiotacticity and molecular weight of the yields were little affected.

The synthesis of high molecular weight polybutene‐1 catalyzed by Cp★ Ti(OBz)3/MAO

A new stereoregular polybutene-1 was synthesized with a novel catalyst precursor η5-pentamethyl cyclopentadienyl titanium tribenzyloxide (Cp★Ti(OBz)3) and methylaluminoxane (MAO). The effects of polymerization conditions on the catalytic activity, molecular weight and stereoregularity of the products were investigated in detail. It was found the catalyst exhibited highest activity of 91.2u2009kgPB mol Ti−1u2009h−1 at Tu2005=u200930u2009°C, Al/Ti = 200. The catalytic activity and molecular weight were sensitive to the Al/Ti (mole/mole), polymerization temperature; they also depended on the Ti concentration. The molecular weight of the products increased with decreasing temperature. The structure and properties of the polybutene-1 were characterized by 13C NMR, GPC, DSC and WAXD. The result showed the microstructure of polybutene-1 extracted by boiling heptane was stereoregular, whereas the ether-soluble fraction was atactic. The molecular weight of polybutene-1 was over one millionu2009gu2005mol−1 and its molecular weight distribution (Mw/Mn) was from 1.1 to 1.2. n n n n© 2001 Society of Chemical Industry

Synthesis and characterization of Elastoplastic poly(styrene-co-ethylene) using novel mono(η5-cyclopentadienyl) titanium and modified methylaluminoxane catalysts

Elastoplastic poly(styrene-co-ethylene) with high molecular weight was synthesized using novel mono(η5-pentamethylcyclopentadienyl)tribenzyloxy titanium [Cp*Ti(OBz)3] complex activated with four types of modified methylaluminoxanes (mMAO) containing different amounts of residual trimethylaluminum (TMA). The ideal mMAO, used as a cocatalyst for the copolymerization of styrene with ethylene, contains TMA approaching to 17.8 wt %. The oxidation states of the titanium-active species in different Cp*Ti(OBz)3/mMAO catalytic systems were determined by the redox titration method. The results show that both active species may exist in the current system, where one [Ti(IV)] gives a copolymer of styrene and ethylene, and the second one [Ti(III)] only produces syndiotactic polystyrene (sPS). Catalytic activity, compositions of copolymerization products, styrene incorporation, and copolymer microstructure depend on copolymerization conditions, including polymerization temperature, Al/Ti, molar ratio, and comonomers feed ratio. The copolymerization products were fractionated by successive solvent extractions with boiling butanone and tetrahydrofuran (THF). The copolymer, chiefly existing in THF-soluble fractions, was confirmed by 13C-NMR, GPC, DSC, and WAXD to be an elastoplastic copolymer with a single glass transition temperature.