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Xuequan Zhang - One of the best experts on this subject based on the ideXlab platform.
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controlling external diphenylcyclohexylphosphine feeding to achieve cis 1 4 syn 1 2 sequence controlled Polybutadienes via cobalt catalyzed 1 3 butadiene polymerization
Journal of Catalysis, 2019Co-Authors: Dirong Gong, Weilun Ying, Junyi Zhao, Yuechao Xu, Carmine Capacchione, Xuequan Zhang, Wenxin Li, Alfonso GrassiAbstract:Abstract Microstructure and unit sequence are critical parameters that determine the properties of Polybutadiene materials. In this contribution, we have reported the syntheses, characterization of 6-(di-tert-butyl-phosphine) amine fused 2-R-pyridine compounds (R = 1′H-oxazoline (L1); 4′,4′-dimethyl oxazoline (L2); 4′-isopropyl oxazoline (L3) supported cobalt dichloride complexes and their performances in regio-selectivity, sequence and molecular weight controlled polymerization of butadiene. In combination with MMAO, the cobalt-mediated polymerization displays many characteristics of a living and cis-1,4 polymerization system over a wide temperature window of 0–80 °C. We show it is possible to tune the number average molecular weight in the range of 152–164 kg/mol with narrow MWD values of 1.04–1.34. The steric bulkiness on the catalysts has detrimental effect on the polymerization rate, (kobs(Co1, substituent free) of 0.037 L/mol·min. >Kobs(Co3, isopropyl) of 0.030 L/mol·min. >Kobs(Co2, dimethyl) to 0.024 L/mol·min.). With diphenylcyclohexylphosphine (Ph2CyP) as in-situ additive, the cobalt catalyst is highly active in cis-1,4 and 1,2-syndiotactic tunable butadiene polymerization to produce various cis-1,4-block-syn-1,2 Polybutadienes differing in block length. By continuous Ph2CyP feeding, this cobalt catalyst has been applied for the first synthesis of a regiogradient Polybutadiene which starts with a cis-1,4 rich Polybutadiene block and ends with an syn-1,2 rich block where the 1,2 specificity controlled between 28.7 and 88.5 mol%, moderate syndiotacticity (rr) of 49.8–64.5% and controlled molecular weight. The processing and mechanical properties were also evaluated. The phosphine dependent regio-selectivity and sequence controlled polymerization provide an simple and efficient strategy for various cis-1,4-syn-1,2 multi-block and cis-1,4-syn-1,2 regiogradient Polybutadiene with tunable physical and mechanical properties.
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synthesis of high crystalline syndiotactic 1 2 Polybutadienes and study on their reinforcing effect on cis 1 4 Polybutadiene
Polymer, 2017Co-Authors: Huafeng Chen, Dirong Gong, Jingshan Mu, Gengsheng Weng, Yanming Hu, Feng Jiang, Wei Li, Xuequan ZhangAbstract:Abstract A novel compound diethyl acetylphosphonate has been explored as efficient additive in iron based catalyst for stereo-polymerization of 1,3-butadiene to afford high crystalline 1,2-syndiotactic Polybutadiene. Excellent 1,2 selectivity in range of 91.0–98.4% with controllable crystallinity has been achieved at high catalytic efficiency in wide ranges of cocatalyst and additive feeding as well as at large temperature scope. As reinforcing agent, two crystalline polymers differing in crystallinity 4.4% and 51.9% are blended and co-cured with cis-1,4 Polybutadiene (PB) with 10 wt-%, providing samples PB1 and PB2, respectively. SEM from the sample fracturesurface shows the s-PBD particles are intimately mixed and homogeneously dispersed in PB matrix due to the strong interfacial interaction. The analysis of the mechanical properties of sample PB2 finds the tensile strength of increases by one-fold and the elongation at break increases by two-fold when head to head comparison to those of the CB filled PB, while the shear modulus G′ and loss factor (tan δ) are as good as those charged with CB. These results highlight the role of s-PBD as reinforcing agent of PB rubber, yielding high performance rubber materials with improved mechanical properties.
Dirong Gong - One of the best experts on this subject based on the ideXlab platform.
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controlling external diphenylcyclohexylphosphine feeding to achieve cis 1 4 syn 1 2 sequence controlled Polybutadienes via cobalt catalyzed 1 3 butadiene polymerization
Journal of Catalysis, 2019Co-Authors: Dirong Gong, Weilun Ying, Junyi Zhao, Yuechao Xu, Carmine Capacchione, Xuequan Zhang, Wenxin Li, Alfonso GrassiAbstract:Abstract Microstructure and unit sequence are critical parameters that determine the properties of Polybutadiene materials. In this contribution, we have reported the syntheses, characterization of 6-(di-tert-butyl-phosphine) amine fused 2-R-pyridine compounds (R = 1′H-oxazoline (L1); 4′,4′-dimethyl oxazoline (L2); 4′-isopropyl oxazoline (L3) supported cobalt dichloride complexes and their performances in regio-selectivity, sequence and molecular weight controlled polymerization of butadiene. In combination with MMAO, the cobalt-mediated polymerization displays many characteristics of a living and cis-1,4 polymerization system over a wide temperature window of 0–80 °C. We show it is possible to tune the number average molecular weight in the range of 152–164 kg/mol with narrow MWD values of 1.04–1.34. The steric bulkiness on the catalysts has detrimental effect on the polymerization rate, (kobs(Co1, substituent free) of 0.037 L/mol·min. >Kobs(Co3, isopropyl) of 0.030 L/mol·min. >Kobs(Co2, dimethyl) to 0.024 L/mol·min.). With diphenylcyclohexylphosphine (Ph2CyP) as in-situ additive, the cobalt catalyst is highly active in cis-1,4 and 1,2-syndiotactic tunable butadiene polymerization to produce various cis-1,4-block-syn-1,2 Polybutadienes differing in block length. By continuous Ph2CyP feeding, this cobalt catalyst has been applied for the first synthesis of a regiogradient Polybutadiene which starts with a cis-1,4 rich Polybutadiene block and ends with an syn-1,2 rich block where the 1,2 specificity controlled between 28.7 and 88.5 mol%, moderate syndiotacticity (rr) of 49.8–64.5% and controlled molecular weight. The processing and mechanical properties were also evaluated. The phosphine dependent regio-selectivity and sequence controlled polymerization provide an simple and efficient strategy for various cis-1,4-syn-1,2 multi-block and cis-1,4-syn-1,2 regiogradient Polybutadiene with tunable physical and mechanical properties.
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preparation and property investigation of chain end functionalized cis 1 4 Polybutadienes via de polymerization and cross metathesis of cis 1 4 Polybutadienes
Polymer Chemistry, 2019Co-Authors: Weilun Ying, Alfonso Grassi, Dirong GongAbstract:The transformation of cis-1,4-Polybutadiene (PBD) to chain end functionalized propyltriethoxysilane (PBD-Si(OEt)3), trimethylsilane (PBD-SiMe3), phosphate (PBD-Phosphate), di-tert-butylphenol (PBD-Phenol) and propane epoxide (PBD-PO) cis-1,4-Polybutadienes via depolymerization by the Grubbs (II) catalyst and tandem cross metathesis employment of the corresponding chain transfer reagents (CTAs) has been developed. The formation of difunctionalized cis-1,4 Polybutadiene (DF) with controlled molecular weight takes place, along with minor amounts of a mono-functionalized polymer (MF) and a non-functionalized polymer (NF) as evidenced by NMR, IR, GPC and MALDI-TOF. The precise cis-1,4 regiocontrol of functionalized rubber leads to further investigation of thermal-mechanical properties of elastomers. The PBD-Phosphate and PBD-Phenol exhibit enhanced thermal properties when the decomposition onset temperature was increased and the decomposition rate was also decreased compared to those of pure cis-1,4 Polybutadiene. PBD-Si(OEt)3 was hydrolyzed on SiO2 and the resultant product was utilized as a compatibilizer for improving the interfacial interaction between filler SiO2 and matrix cis-1,4 Polybutadiene. As a result, improvements of the resultant vulcanizate properties regarding elongation at break, tensile strength and loss factor are observed. The established knowledge of the correlation of functional groups in the chain end with thermal-physical properties could provide guidelines to develop high performance rubber materials from various conjugated diene elastomers.
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synthesis of high crystalline syndiotactic 1 2 Polybutadienes and study on their reinforcing effect on cis 1 4 Polybutadiene
Polymer, 2017Co-Authors: Huafeng Chen, Dirong Gong, Jingshan Mu, Gengsheng Weng, Yanming Hu, Feng Jiang, Wei Li, Xuequan ZhangAbstract:Abstract A novel compound diethyl acetylphosphonate has been explored as efficient additive in iron based catalyst for stereo-polymerization of 1,3-butadiene to afford high crystalline 1,2-syndiotactic Polybutadiene. Excellent 1,2 selectivity in range of 91.0–98.4% with controllable crystallinity has been achieved at high catalytic efficiency in wide ranges of cocatalyst and additive feeding as well as at large temperature scope. As reinforcing agent, two crystalline polymers differing in crystallinity 4.4% and 51.9% are blended and co-cured with cis-1,4 Polybutadiene (PB) with 10 wt-%, providing samples PB1 and PB2, respectively. SEM from the sample fracturesurface shows the s-PBD particles are intimately mixed and homogeneously dispersed in PB matrix due to the strong interfacial interaction. The analysis of the mechanical properties of sample PB2 finds the tensile strength of increases by one-fold and the elongation at break increases by two-fold when head to head comparison to those of the CB filled PB, while the shear modulus G′ and loss factor (tan δ) are as good as those charged with CB. These results highlight the role of s-PBD as reinforcing agent of PB rubber, yielding high performance rubber materials with improved mechanical properties.
Erhard W. Fischer - One of the best experts on this subject based on the ideXlab platform.
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structure of Polybutadienes synthesized with a new catalyst system 2 blends of trans and cis 1 4 Polybutadiene
Macromolecular Chemistry and Physics, 2001Co-Authors: E. M. Antipov, Evguenia A Mushina, Manfred Stamm, Erhard W. FischerAbstract:The structure, composition and temperature behaviour of Polybutadienes prepared with binuclear metal complex catalysts immobilized on a solid carrier are investigated by differential scanning calorimetry, infra-red spectroscopy and X-ray scattering. Polybutadienes of nascent structure are blends of trans-1,4- and cis-1,4-homopolymers, whereas 1,2-units are randomly distributed in both macromolecules. The blends exhibit two-step melting characteristics for the crystalline trans-1,4-Polybutadiene: the low-temperature transition from the monoclinic crystal form to the pseudohexagonal mesophase and the high-temperature transition from mesophase to the melt. A bimodal character of the endothermic maximum in DSC traces was observed for the former transition. In addition, it was shown that the nascent blend treated by hot toluene posseses a three-phase structure and contains, besides the well-known trans-1,4-Polybutadiene crystalline and amorphous phases, an additional phase component of unknown structure.
Yusuf Yagci - One of the best experts on this subject based on the ideXlab platform.
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combining polybenzoxazines and Polybutadienes via simultaneous inverse and direct vulcanization for flexible and recyclable thermosets by polysulfide dynamic bonding
Polymer Chemistry, 2019Co-Authors: Buket Akkus, Baris Kiskan, Yusuf YagciAbstract:In this work, we report a novel approach to combine two structurally diverse polymers, namely polybenzoxazine and Polybutadiene by simultaneous inverse and direct vulcanization. The process is based on mixing elemental sulphur, mono-functional benzoxazines and Polybutadienes (PB) in various ratios, and heating up to 180 °C. Inverse vulcanization between sulphur atoms and oxazine rings triggered ring-opening polymerization of benzoxazines and vulcanization of PB proceeded concomitantly. Flexible films were cast in Teflon molds by using PB in high amounts in formulations. These films were cut into pieces and subjected to a recycling process at 180 °C for up to 5 cycles through polysulfide dynamic bonding. The extent of recovery of the films was quantified by tensile tests. Spectral characterization and thermal behavior of the films were also investigated before and after the recycling process.
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post modification of Polybutadienes by photoinduced hydrogen abstraction from benzoxazines and their thermally activated curing
Macromolecules, 2016Co-Authors: Mustafa Arslan, Baris Kiskan, Yusuf YagciAbstract:Side-chain benzoxazine functional Polybutadienes was synthesized by photoinduced hydrogen abstraction process. First, photoactive benzoxazines having both chromophoric carbonyl and hydrogen donating sites were synthesized using vanillin or 4-hydroxybenzophenone by conventional benzoxazine synthesis methodology. Irradiation of neat Polybutadiene (PB) in the presence of the corresponding benzoxazines, namely benzophenone benzoxazine (BPh-ptol) and vanillin benzoxazine (Van-a) under 300–350 nm light, gave PBs with approximately 4–5 benzoxazine units per chain. Successful modification was confirmed by the spectral and thermal investigations. It is demonstrated that PBs attached with benzoxazines undergo thermally activated curing without any catalyst to form Polybutadiene thermoset with high char yield.
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self curable benzoxazine functional Polybutadienes synthesized by click chemistry
Designed Monomers and Polymers, 2009Co-Authors: Manolya Kukut, Baris Kiskan, Yusuf YagciAbstract:Novel side-chain benzoxazine functional Polybutadiene (PB-benzoxazine) was synthesized by using click chemistry strategy. First, some of double bonds were brominated with Br2 in CCl4 and subsequently converted to azido groups by using NaN3 in DMF. Propargyl benzoxazine was prepared independently by a ring-closure reaction between p-propargyloxy aniline, paraformaldehyde and phenol. Finally, azidofunctionalized Polybutadiene was coupled to propargyl benzoxazine with high efficiency by click chemistry. The spectral and thermal analysis confirmed the presence of benzoxazine functionality in the resulting polymer. It is shown that PB-benzoxazine undergoes thermally activated curing in the absence of any catalyst forming Polybutadiene thermoset with high char yield.
Alfonso Grassi - One of the best experts on this subject based on the ideXlab platform.
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controlling external diphenylcyclohexylphosphine feeding to achieve cis 1 4 syn 1 2 sequence controlled Polybutadienes via cobalt catalyzed 1 3 butadiene polymerization
Journal of Catalysis, 2019Co-Authors: Dirong Gong, Weilun Ying, Junyi Zhao, Yuechao Xu, Carmine Capacchione, Xuequan Zhang, Wenxin Li, Alfonso GrassiAbstract:Abstract Microstructure and unit sequence are critical parameters that determine the properties of Polybutadiene materials. In this contribution, we have reported the syntheses, characterization of 6-(di-tert-butyl-phosphine) amine fused 2-R-pyridine compounds (R = 1′H-oxazoline (L1); 4′,4′-dimethyl oxazoline (L2); 4′-isopropyl oxazoline (L3) supported cobalt dichloride complexes and their performances in regio-selectivity, sequence and molecular weight controlled polymerization of butadiene. In combination with MMAO, the cobalt-mediated polymerization displays many characteristics of a living and cis-1,4 polymerization system over a wide temperature window of 0–80 °C. We show it is possible to tune the number average molecular weight in the range of 152–164 kg/mol with narrow MWD values of 1.04–1.34. The steric bulkiness on the catalysts has detrimental effect on the polymerization rate, (kobs(Co1, substituent free) of 0.037 L/mol·min. >Kobs(Co3, isopropyl) of 0.030 L/mol·min. >Kobs(Co2, dimethyl) to 0.024 L/mol·min.). With diphenylcyclohexylphosphine (Ph2CyP) as in-situ additive, the cobalt catalyst is highly active in cis-1,4 and 1,2-syndiotactic tunable butadiene polymerization to produce various cis-1,4-block-syn-1,2 Polybutadienes differing in block length. By continuous Ph2CyP feeding, this cobalt catalyst has been applied for the first synthesis of a regiogradient Polybutadiene which starts with a cis-1,4 rich Polybutadiene block and ends with an syn-1,2 rich block where the 1,2 specificity controlled between 28.7 and 88.5 mol%, moderate syndiotacticity (rr) of 49.8–64.5% and controlled molecular weight. The processing and mechanical properties were also evaluated. The phosphine dependent regio-selectivity and sequence controlled polymerization provide an simple and efficient strategy for various cis-1,4-syn-1,2 multi-block and cis-1,4-syn-1,2 regiogradient Polybutadiene with tunable physical and mechanical properties.
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preparation and property investigation of chain end functionalized cis 1 4 Polybutadienes via de polymerization and cross metathesis of cis 1 4 Polybutadienes
Polymer Chemistry, 2019Co-Authors: Weilun Ying, Alfonso Grassi, Dirong GongAbstract:The transformation of cis-1,4-Polybutadiene (PBD) to chain end functionalized propyltriethoxysilane (PBD-Si(OEt)3), trimethylsilane (PBD-SiMe3), phosphate (PBD-Phosphate), di-tert-butylphenol (PBD-Phenol) and propane epoxide (PBD-PO) cis-1,4-Polybutadienes via depolymerization by the Grubbs (II) catalyst and tandem cross metathesis employment of the corresponding chain transfer reagents (CTAs) has been developed. The formation of difunctionalized cis-1,4 Polybutadiene (DF) with controlled molecular weight takes place, along with minor amounts of a mono-functionalized polymer (MF) and a non-functionalized polymer (NF) as evidenced by NMR, IR, GPC and MALDI-TOF. The precise cis-1,4 regiocontrol of functionalized rubber leads to further investigation of thermal-mechanical properties of elastomers. The PBD-Phosphate and PBD-Phenol exhibit enhanced thermal properties when the decomposition onset temperature was increased and the decomposition rate was also decreased compared to those of pure cis-1,4 Polybutadiene. PBD-Si(OEt)3 was hydrolyzed on SiO2 and the resultant product was utilized as a compatibilizer for improving the interfacial interaction between filler SiO2 and matrix cis-1,4 Polybutadiene. As a result, improvements of the resultant vulcanizate properties regarding elongation at break, tensile strength and loss factor are observed. The established knowledge of the correlation of functional groups in the chain end with thermal-physical properties could provide guidelines to develop high performance rubber materials from various conjugated diene elastomers.