In this work, the effect of the fullerene（C_（60）） weight fraction and PB-C_（60） interaction on the glass transition temperature（T_g） of polymer chains has been systemically investigated by adopting the united ...In this work, the effect of the fullerene（C_（60）） weight fraction and PB-C_（60） interaction on the glass transition temperature（T_g） of polymer chains has been systemically investigated by adopting the united atom model of cis-1,4-poly（butadiene）（cis-PB）. Various chain dynamics properties, such as atom translational mobility, bond/segment reorientation dynamics, torsional dynamics, conformational transition rate and dynamic heterogeneity of the cis-PB chains, are analyzed in detail. It is found that T_g could be affected by the C_（60） weight fraction due to its inhibition effect on the mobility of the cis-PB chains. However, T_g is different, which depends on different dynamics scales. Among the chain dynamics properties, T_g is the lowest from atom translational mobility, while it is the highest from the dynamic heterogeneity. In addition, T_g can be more clearly distinguished from the dynamic heterogeneity; however, the conformational transition rate seems to be not very sensitive to the C_（60） weight fraction compared with others. For pure cis-PB chains, T_g and the activation energy in this work can be compared with those of other polymers. In addition, the temperature dependence of the dynamic properties has different Arrhenius behaviors above and below T_g. The activation energy below T_g is lower than that above T_g. This work can help to understand the effect of the C_（60） on the dynamic properties and glass transition temperature of the cis-PB chains from different scales.展开更多
The mechanical properties and phase morphologies of cis-1,4-butadiene rubber（BR） blended with polyethylene（PE） at different blend ratios were studied. The tensile test results show that the PE exhibits excellent r...The mechanical properties and phase morphologies of cis-1,4-butadiene rubber（BR） blended with polyethylene（PE） at different blend ratios were studied. The tensile test results show that the PE exhibits excellent reinforcing capabilities towards BR. Blending BR with PE results in a remarkable enhancement of tensile strength, modulus and the elongation at break simultaneously. An increment of tensile strength from 1.11 MPa to 16.26 MPa was achieved by incorporation of 40 wt% PE in the blends. The modulus and elongation at break of 40/60 PE/BR blends are also about 5 times higher than those of the pure BR treated under exactly the same conditions. The tear test indicates that the tear strength also increases with the increase of PE content. It reaches 58.38 MPa for the 40/60 PE/BR blend, which is approximately 10 times higher than that of the pure BR. Morphological study demonstrates that the PE forms elongated microdomains finely dispersed in the BR matrix when its content is over 30 wt%, which corresponds to the remarkably enhanced mechanical properties.According to the results, reinforcement mechanism of PE toward BR dependent on the microstructure has been discussed and two different mechanisms have been proposed.展开更多
NMR imaging has become a routine technique for medical and biological science and is finding increasing application to materials research. It is a nondestructive and noninvasive technique used to study properties of v...NMR imaging has become a routine technique for medical and biological science and is finding increasing application to materials research. It is a nondestructive and noninvasive technique used to study properties of various types of materials, including solvent filled ceramics, oil reservoir cores and elastic polymers.展开更多
The aryldiimine NCN-pincer stabilized neodymium dichloride combined with aluminum alkyls established a new type of homogeneous binary neutral Ziegler-Natta catalyst system.This system exhibited high activity and high ...The aryldiimine NCN-pincer stabilized neodymium dichloride combined with aluminum alkyls established a new type of homogeneous binary neutral Ziegler-Natta catalyst system.This system exhibited high activity and high cis-1,4 selectivity for the polymerization of isoprene (Tp=20 °C,98.2%;Tp=-20 °C,】 99%).Such catalytic performances remained under a broad range of polymerization temperatures and monomer-to-neodymium ratios (from 500 to 8000),reaching high number-average molecular weight (Mn=1582 kg/mol) and relatively narrow molecular weight distribution (PDI=1.68),which was,however,influenced by the amount and bulkiness of aluminum alkyls.Dynamic investigation of the polymerization was performed,which showed the number-average molecular weight of the resultant polyisoprene had an almost linear correlation with the conversion,suggesting,in some degree,the polymerization with this catalytic system was controllable.展开更多
基金financial supports from the start-up funding of Beijing University of Chemical Technology(BUCT)for excellent introduced talentsthe Fundamental Research Funds for the Central Universities(JD1711)
文摘In this work, the effect of the fullerene（C_（60）） weight fraction and PB-C_（60） interaction on the glass transition temperature（T_g） of polymer chains has been systemically investigated by adopting the united atom model of cis-1,4-poly（butadiene）（cis-PB）. Various chain dynamics properties, such as atom translational mobility, bond/segment reorientation dynamics, torsional dynamics, conformational transition rate and dynamic heterogeneity of the cis-PB chains, are analyzed in detail. It is found that T_g could be affected by the C_（60） weight fraction due to its inhibition effect on the mobility of the cis-PB chains. However, T_g is different, which depends on different dynamics scales. Among the chain dynamics properties, T_g is the lowest from atom translational mobility, while it is the highest from the dynamic heterogeneity. In addition, T_g can be more clearly distinguished from the dynamic heterogeneity; however, the conformational transition rate seems to be not very sensitive to the C_（60） weight fraction compared with others. For pure cis-PB chains, T_g and the activation energy in this work can be compared with those of other polymers. In addition, the temperature dependence of the dynamic properties has different Arrhenius behaviors above and below T_g. The activation energy below T_g is lower than that above T_g. This work can help to understand the effect of the C_（60） on the dynamic properties and glass transition temperature of the cis-PB chains from different scales.
基金financially supported by the National Natural Science Foundation of China(Nos.51221002 and 21174014)
文摘The mechanical properties and phase morphologies of cis-1,4-butadiene rubber（BR） blended with polyethylene（PE） at different blend ratios were studied. The tensile test results show that the PE exhibits excellent reinforcing capabilities towards BR. Blending BR with PE results in a remarkable enhancement of tensile strength, modulus and the elongation at break simultaneously. An increment of tensile strength from 1.11 MPa to 16.26 MPa was achieved by incorporation of 40 wt% PE in the blends. The modulus and elongation at break of 40/60 PE/BR blends are also about 5 times higher than those of the pure BR treated under exactly the same conditions. The tear test indicates that the tear strength also increases with the increase of PE content. It reaches 58.38 MPa for the 40/60 PE/BR blend, which is approximately 10 times higher than that of the pure BR. Morphological study demonstrates that the PE forms elongated microdomains finely dispersed in the BR matrix when its content is over 30 wt%, which corresponds to the remarkably enhanced mechanical properties.According to the results, reinforcement mechanism of PE toward BR dependent on the microstructure has been discussed and two different mechanisms have been proposed.
文摘NMR imaging has become a routine technique for medical and biological science and is finding increasing application to materials research. It is a nondestructive and noninvasive technique used to study properties of various types of materials, including solvent filled ceramics, oil reservoir cores and elastic polymers.
基金supported by the National Natural Science Foundation of China (20674081,20934006) the Ministry of Science and Technology of China (2005CB623802,2009AA03Z501).
文摘The aryldiimine NCN-pincer stabilized neodymium dichloride combined with aluminum alkyls established a new type of homogeneous binary neutral Ziegler-Natta catalyst system.This system exhibited high activity and high cis-1,4 selectivity for the polymerization of isoprene (Tp=20 °C,98.2%;Tp=-20 °C,】 99%).Such catalytic performances remained under a broad range of polymerization temperatures and monomer-to-neodymium ratios (from 500 to 8000),reaching high number-average molecular weight (Mn=1582 kg/mol) and relatively narrow molecular weight distribution (PDI=1.68),which was,however,influenced by the amount and bulkiness of aluminum alkyls.Dynamic investigation of the polymerization was performed,which showed the number-average molecular weight of the resultant polyisoprene had an almost linear correlation with the conversion,suggesting,in some degree,the polymerization with this catalytic system was controllable.
