| A novel rare earth catalyst composed of neodymium tricarboxylate (RE), cocatalyst Al(i-Bu)3(Al), and chlorinating agents (CL and TEE) was prepared. The homo-polymerization of styrene (St) and butadiene (Bd), sequencial copolymerization of St and Bd were carried out. The effects of the catalyst system and reaction conditions were studied. The microstructure, composition, sequence and morphology of the copolymer were characterized by FTIR,1H-NMR,13C-NMR, DSC, TEM and AFM. The molecular weight and its distribution of the copolymer were determined by GPC. The results are shown as follows:1. The preferable catalyst system used in the homo-polymerization of St was prepared with TEE/RE=0.8-1.2(molar ratio), CL/RE=20～90(molar ratio) and Al/RE=10～20(molar ratio). The preferable RE/St was9.0×10-4～2.3×10-3(molar ratio). The rate of the propagation is first-order dependent on the monomer concentration and the activity energy of apparent propagation is50KJ·mol-1. A crystalline PS with Mw of1.0×104g·mol-1～8.0×104g·mol-1and Mw/Mn of1.5were obtained with the preferable catalyst system. Tg and Tm of the crystalline PS with some stereo-regularity configurations in PS segment were70℃～100℃and150℃～270℃respectively.2. The preferable catalyst system used in the homo-polymerization of Bd was prepared with TEE/RE=0.8-1.6(molar ratio), CL/RE=20℃50(molar ratio) and Al/RE=14℃20(molar ratio). The catalyst system was aged at15℃～30℃for less than6h. The preferable RE/Bd was2.5×10-4～4.0×10-4(molar ratio). The activity energy of apparent propagation is27.4KJ·mol-1. A high cis PB (cis-1,4>98.0%(mol)) with Mw of around5.5X105g·mol-1and Mw/Mn of around2.0were obtained with the preferable catalyst system. Tg and Tm of the high cis PB were around-110℃and-10℃respectively. Tensile strength,300%modulus and elongation at break were improved by37%,17%and16%respectively compared with the corresponding Ni-PB vulcanizate. The excellent low temperature performance, lower rolling resistance and energy loss were gained as well.3. Di-block copolymer (SB) was prepared with block efficiency of62%-77%. SB could be divided into SB1(93%(wt)) that can dissolve in tetrahydrofuran (THF) and SB2(7%(wt)) that cannot dissolve in THF. Distribution of SB1was bimodal, Mp of the higher and lower molecular weight parts were around9×105g·mol-1and3×104g·mol-1respectively. PS segments were distributed on the copolymer chains that with different molecular weight and St content were12.9%(mol)-22.6%(mol). Cis-1,4content in Bd units were98.0%(mol). Tg and Tm of PB segment were-107℃and-13℃respectively; Tg and Tm of PS segment were95℃and251℃respectively. Distribution of SB2was bimodal, Mpof the higher and lower molecular weight parts were around2.2×105g·mol-1and2.0×104·mol-1respectively. Tg and Tm of PB segment were-108℃and-13℃respectively; Tg and Tm of PS segment were71℃and258℃respectively.4. Tri-block copolymerization of St and Bd was preliminary studied. Distribution of SBS was bimodal, Mp of the higher and lower molecular weight parts were around9×105g·mol-1and5×104g·mol-1respectively. PS segments were distributed on the copolymer chains that with different molecular weight and St content were9.6%(mol)-22.3%(mol). Cis-1,4content in Bd units were98.0%(mol). Tg and Tm of PB segment were-107℃and-13℃respectively; Tg and Tm of PS segment were73℃and251℃respectively.5. Tensile strength, tear strength and elongation at break of SB were improved by5.8%,30.0%and26.8%respectively compared with the corresponding Ni-PB vulcanizate. The wet-skid resistance was improved while kept the excellent low temperature performance.6. GPPS/SB blends were prepared by adding3-5%(wt) SB into general purpose polystyrene (GPPS). PB domains of10nm-50nm with a blurry interface were tethered by continuous PS domains. The fracture surface of the tensile test piece of GPPS was relatively smooth while the fractography of patch patterns separated by river patterns was formed when the tensile specimens of GPPS/SB blends were broken. Tensile strength and elongation at break of GPPS were improved by130%and500%-1300%respectively. The tensile strength of GPPS could be maintained or even improved.7. A novel HIPS product with bulk polymerization technique in one-pot was preliminary conducted. Round and stripe PB domains with the size of20nm～500nm were tethered by continuous PS domains. The interface of PB and PS phases was blurry and the interpenetrating network was formed during the copolymerization. HIPS products were expected to be a novel material with excellent intensity and toughness. |
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