The phase transition from tetragonal form II to hexagonal form I was studied for the butene-1/ethylene and butene-1/1,5- hexadiene random copolymers, which have comparable molecular weight but distinct linear ethylene...The phase transition from tetragonal form II to hexagonal form I was studied for the butene-1/ethylene and butene-1/1,5- hexadiene random copolymers, which have comparable molecular weight but distinct linear ethylene and ringlike methylene-1,3- cyclopentane （MCP） structural co-units, respectively. It is known that this solid phase transition follows the nucleation-growth mechanism, so the stepwise annealing protocol was utilized to investigate the influences of co-units on the optimal nucleation and growth temperatures. Compared with optimal nucleation and growth temperatures of-10 and 3 5 ℃, respectively, in polybutene-1 homopolymer, two butene-1/ethylene copolymers with 1.5 mol% and 4.3 mol% co-units have the slightly lower optimal nucleation temperature of-15 ℃ but much higher optimal growth temperature of 50 ℃. Clearly, the effect of ethylene co-unit is more significant on varying optimal temperature for growth than for nucleation. Furthermore, when the incorporated co-unit is ringlike MCP, the optimal nucleation temperature is -15 ℃ for 2.15 mol% co-units, the same with above BE copolymers, but -13 ℃ for a very low concentration of 0.65 mol%. Interestingly, the optimal growth temperature of butene-1/1,5-hexadiene copolymers with 0.65 mo1%-2.15 mol% MCP co- units increases to 55 ℃, which is also independent on co-unit concentration. These obtained values of optimal temperatures provide crucial parameters for rapid II-I phase transition.展开更多
The dimethylpyridylamidohafnium catalyst was used to synthesize 1-butene/cyclohexene and 1-butene/vinylcyclohexane random copolymers,which have extra six-membered cyclic co-units in main chain and side chain,respectiv...The dimethylpyridylamidohafnium catalyst was used to synthesize 1-butene/cyclohexene and 1-butene/vinylcyclohexane random copolymers,which have extra six-membered cyclic co-units in main chain and side chain,respectively.For the obtained copolymers of different incorporations,the crystallization from amorphous melt and the solid phase transition from tetragonal to trigonal phases were investigated with differential scanning calorimetry.Both of the incorporated cyclic co-units decrease the crystallization kinetics,but the presence of cyclohexene keeps the melting temperature of copolymers constant.Interestingly,the strong memory effect of crystallization can appear at the elevated temperature even above the equilibrium melting temperature,as the content of co-units was increased.The 1-butene/vinylcyclohexane copolymer with 1.52 mol%co-units exhibits a rather strong memory effect with the broad Domain Ila width of 43℃and the crystallization temperature raising of 24℃.Furthermore,the transition of tetragonal phase into trigonal phase was also explored for different co-units and incorporations.It was found that both of the cyclohexene co-units and vinylcyclohexane co-units effectively slow down the kinetics of phase transition.However,the vinylcyclohexane co-units have a much higher efficiency in suppressing phase transition than the cyclohexene co-units,where 0.53 mol%vinylcyclohexane can com-pletely stop phase transition within 1320 h.Considering the fact that copolymers with vinylcyclohexane co-units actually have lower glass transition temperatures,it was indicated that the suppression of phase transition is also largely influenced by the steric co-units in the side chain for the helical and positional adjustments,not only by the segmental mobility.展开更多
采用集合论的方法给出了单位模糊集合和二型模糊集合及其在一点的限制等定义,使得二型模糊集合更易于理解.通过定义嵌入单位模糊集合来描述一般二型模糊集合,并给出离散、半连通二型模糊集合的表达式.根据论域、主隶属度及隶属函数的特...采用集合论的方法给出了单位模糊集合和二型模糊集合及其在一点的限制等定义,使得二型模糊集合更易于理解.通过定义嵌入单位模糊集合来描述一般二型模糊集合,并给出离散、半连通二型模糊集合的表达式.根据论域、主隶属度及隶属函数的特性将二型模糊集合分为四种类型:离散、半连通、连通及复合型,并根据连通的特点将连通二型模糊集合分为单连通及多连通两类.利用支集的闭包(Closure of support,CoS)划分法表述主隶属度及区间二型模糊集合.提出了CoS二、三次划分法分别来表述单、复连通二型模糊集合,并使每一个子区域的上下边界及次隶属函数在该子区域上的限制分别具有相同的解析表述式.最后,探讨了二型模糊集合在一点的限制、主隶属度、支集、嵌入单位模糊集合之间的关系.展开更多
基金supported by the National Natural Science Foundation of China(Nos.51573132 and 51633009)Tianjin Natural Science Foundation(No.16JCQNJC02700)
文摘The phase transition from tetragonal form II to hexagonal form I was studied for the butene-1/ethylene and butene-1/1,5- hexadiene random copolymers, which have comparable molecular weight but distinct linear ethylene and ringlike methylene-1,3- cyclopentane （MCP） structural co-units, respectively. It is known that this solid phase transition follows the nucleation-growth mechanism, so the stepwise annealing protocol was utilized to investigate the influences of co-units on the optimal nucleation and growth temperatures. Compared with optimal nucleation and growth temperatures of-10 and 3 5 ℃, respectively, in polybutene-1 homopolymer, two butene-1/ethylene copolymers with 1.5 mol% and 4.3 mol% co-units have the slightly lower optimal nucleation temperature of-15 ℃ but much higher optimal growth temperature of 50 ℃. Clearly, the effect of ethylene co-unit is more significant on varying optimal temperature for growth than for nucleation. Furthermore, when the incorporated co-unit is ringlike MCP, the optimal nucleation temperature is -15 ℃ for 2.15 mol% co-units, the same with above BE copolymers, but -13 ℃ for a very low concentration of 0.65 mol%. Interestingly, the optimal growth temperature of butene-1/1,5-hexadiene copolymers with 0.65 mo1%-2.15 mol% MCP co- units increases to 55 ℃, which is also independent on co-unit concentration. These obtained values of optimal temperatures provide crucial parameters for rapid II-I phase transition.
基金the National Natural Science Foundation of China(Nos.51873151 and 52022065).
文摘The dimethylpyridylamidohafnium catalyst was used to synthesize 1-butene/cyclohexene and 1-butene/vinylcyclohexane random copolymers,which have extra six-membered cyclic co-units in main chain and side chain,respectively.For the obtained copolymers of different incorporations,the crystallization from amorphous melt and the solid phase transition from tetragonal to trigonal phases were investigated with differential scanning calorimetry.Both of the incorporated cyclic co-units decrease the crystallization kinetics,but the presence of cyclohexene keeps the melting temperature of copolymers constant.Interestingly,the strong memory effect of crystallization can appear at the elevated temperature even above the equilibrium melting temperature,as the content of co-units was increased.The 1-butene/vinylcyclohexane copolymer with 1.52 mol%co-units exhibits a rather strong memory effect with the broad Domain Ila width of 43℃and the crystallization temperature raising of 24℃.Furthermore,the transition of tetragonal phase into trigonal phase was also explored for different co-units and incorporations.It was found that both of the cyclohexene co-units and vinylcyclohexane co-units effectively slow down the kinetics of phase transition.However,the vinylcyclohexane co-units have a much higher efficiency in suppressing phase transition than the cyclohexene co-units,where 0.53 mol%vinylcyclohexane can com-pletely stop phase transition within 1320 h.Considering the fact that copolymers with vinylcyclohexane co-units actually have lower glass transition temperatures,it was indicated that the suppression of phase transition is also largely influenced by the steric co-units in the side chain for the helical and positional adjustments,not only by the segmental mobility.
文摘采用集合论的方法给出了单位模糊集合和二型模糊集合及其在一点的限制等定义,使得二型模糊集合更易于理解.通过定义嵌入单位模糊集合来描述一般二型模糊集合,并给出离散、半连通二型模糊集合的表达式.根据论域、主隶属度及隶属函数的特性将二型模糊集合分为四种类型:离散、半连通、连通及复合型,并根据连通的特点将连通二型模糊集合分为单连通及多连通两类.利用支集的闭包(Closure of support,CoS)划分法表述主隶属度及区间二型模糊集合.提出了CoS二、三次划分法分别来表述单、复连通二型模糊集合,并使每一个子区域的上下边界及次隶属函数在该子区域上的限制分别具有相同的解析表述式.最后,探讨了二型模糊集合在一点的限制、主隶属度、支集、嵌入单位模糊集合之间的关系.
