Polybutene-1(PB-1) is a semi-crystalline polymer with excellent mechanical properties. However, its practical application is significantly hindered by the slow Form Ⅱ-Ⅰ transition, which can take up to several days ...Polybutene-1(PB-1) is a semi-crystalline polymer with excellent mechanical properties. However, its practical application is significantly hindered by the slow Form Ⅱ-Ⅰ transition, which can take up to several days to complete. While prior research established that long-chain branching(LCB) structures synthesized via ω-alkenylmethyldichlorosilane copolymerization-hydrolysis(ACH) chemistry markedly accelerate this transition, this work demonstrates that H-shaped LCB structures constructed through copolymerization with 1,9-decadiene exhibit the capability to facilitate Form Ⅱ-Ⅰ transition in most systems evaluated herein. However, low branching efficiency concurrently generates extended alkyl pendant chains, which impose pronounced steric-hindrance-driven suppression on the transition kinetics, thereby substantially diminishing the net acceleration effect of the LCB structures, even resulting in a net retardation effect in certain systems. Notably, a significant synergistic acceleration effect emerged between the H-shaped LCB structures and propylene comonomer units. These findings confirm that the H-shaped LCB structures play a role in promoting the Form II-I transformation process, which is independent of the synthetic pathways, thereby providing more strategies for addressing the long-standing processing problems of PB-1.展开更多
The slow phase transition from formⅡto formⅠhas always been an important factor that restricts the processing and application of polybutene-1(PB-1).After extensive efforts,a set of effective methods for promoting th...The slow phase transition from formⅡto formⅠhas always been an important factor that restricts the processing and application of polybutene-1(PB-1).After extensive efforts,a set of effective methods for promoting the phase transition rate in PB-1 was established by adjusting the crystallization,nucleation,and growth temperatures.Nevertheless,low-molecular-weight PB-1(LMWPB-1)faces challenges because this method requires a low crystallization temperature,which is difficult to achieve during extrusion processing.In this study,we attempted to increase the phase transition rate in PB-1 by changing the annealing temperature after processing rather than the crystallization temperature in the classical scheme.The results indicated that regardless of low-or high-molecular-weight PB-1,repeated annealing between 0 and 90℃could also promote formⅡto formⅠphase transition.The initial content of formⅠincreased with the heating and cooling cycles.The half-time of the phase transition(t_(1/2))was also shortened after heating/cooling.After 100 heating/cooling cycles,t_(1/2) was reduced to one-quarter of that without annealing,which had almost the same effect as the crystallization temperature at 25℃in promoting the phase transition.This study indicates that annealing after processing is also an important factor affecting the phase transition of PB-1,and should receive sufficient attention.展开更多
For the solid-solid transformation from formⅡto formⅠof isotactic polybutene-1(iPB),the temperature dependence of formⅠnucleation and growth was deemed to control the transformation process.However,the relationship...For the solid-solid transformation from formⅡto formⅠof isotactic polybutene-1(iPB),the temperature dependence of formⅠnucleation and growth was deemed to control the transformation process.However,the relationship between formⅠformation and formⅡdisappearance in the transformation process is not clear.In this work,the spontaneous crystal transformation from formⅡtoⅠof iPB with 81 mol%mmmm sequence concentration is studied firstly by tracking the two processes,the decay of formⅡand the yielding of formⅠin a wide range of temperature spanning from 0℃to 50℃and in a long transformation time ranging from 5 min to 65 days with in situ FTIR and WAXD.Unlike the literature reports,the decay rate of formⅡis firstly found to be lower than the yielding rate of formⅠat all studied temperatures,especially at low transition temperature.This is attributed to the amorphous chains which locate near crystal lamella participating into the nucleation of formⅡ.The regular chain folding and growth of i PB formⅠfrom amorphous chains containing short isotactic sequences also lead to an increase in crystallinity of formⅠcompared with that of initial formⅡcrystallized at 60℃.An increase in the annealing temperature results in decrease in crystallinity and increase in lamellae thickness of i PB formⅠ.展开更多
Isotactic polybutene-1 (iPB-1) is a semi-crystalline polymer with polymorph and puzzled structural transitions. The stable form I of iPB-1 with excellent physical and mechanical properties can hardly be obtained direc...Isotactic polybutene-1 (iPB-1) is a semi-crystalline polymer with polymorph and puzzled structural transitions. The stable form I of iPB-1 with excellent physical and mechanical properties can hardly be obtained directly from the melt;instead, metastable form II will spontaneously and slowly transform into form I. Bypassing the unstable form II formation is of great significance in polymer processing, which inspires extensive research on seeking the pathways to direct formation of form I. Methods for accelerating form II to I transition are another main focus in terms of practical approach for directly obtaining form I. Taking advantage of the solvent, an ultrafast transition of iPB-1 from form II to I within minutes has been achieved at room temperature. Such an ultrafast transition is detected after treating with dichloromethane (DCM) at 30 ℃, though the framework of isothermally crystalized iPB-1 spherulite morphology could not be fully modified. The ultrafast II-I transition of iPB-1 is attributed to the solvent-induced packed-mesophase and temperature-selected chain conformation adjustment.This ultrafast transition would shed light on understanding the mechanisms of polymorphic transitions in iPB-1.展开更多
Solvent annealing is a facile method for changing the aggregated microstructure and physical properties of polymer materials.In this paper,we addressed the effects of solvent vapor annealing,including chloroform and w...Solvent annealing is a facile method for changing the aggregated microstructure and physical properties of polymer materials.In this paper,we addressed the effects of solvent vapor annealing,including chloroform and water vapor,on the polymorphic transformation in both hot-pressed film and electrospun nonwoven of isotactic polybutene-1(PB-1)by means of in situ Fourier transform infrared spectroscopy(FTIR).The pretty rapid transition rate caused by the increased motion of molecular chains under chloroform vapor is associated with a lowest crystallinity.Also,a decreased crystallinity with the crystal transition occurred in electrospun nonwovens resulting from the relaxation of the stretched molecular chains into amorphous state rather than realignment into crystal form I predominating the crystal transition process.展开更多
The composition and structure of polymer largely determine the properties of its final products.As a novel polymer material,the composition,structure,and properties of the isotactic polypropylene/polybutene-1 in-react...The composition and structure of polymer largely determine the properties of its final products.As a novel polymer material,the composition,structure,and properties of the isotactic polypropylene/polybutene-1 in-reactor alloy(PPIPB alloy)synthesized by sequential two-stage polymerization with Ziegler-Natta catalyst were correlated for the first time in this work.The iPP/PB alloy was fractionated by temperature rising elution fractionation(TREF)in a broad temperature ranged from-30℃to 140℃,and the chain microstructures and sequence distributions of isolated fractions were analyzed by DSC,GPC,13C-NMR,and FTIR.The iPP/IPB alloy was composed of five components,namely high isotactic PB(PB,85.8 wt96),medium isotactic PB(mPB,5.1 wt%),polyl(butene-1)-block propylene copolymers(PB-6 PP,4.1 wt%6)which contained PB and PP blocks with dfferent lengths according to the isolation temperature,isotactic PP(iPP,2.7 wt%6),and atactic PB(aPB,2.3 wt96).Compared to other commercial pipe materials,the P/iPB alloy presented outstanding thermal creep resistance and gas permeability resistance,high strength and low deformation at high temperature,and appropriate flexural strength.The roles of PP and PB-b-PP components in the alloy were interpreted.This work is expected to elucidate the potential application of PPIPB aloy as pipe materials and provide solutions for the design and synthesis of high performance pipe materials.展开更多
Polybutene-1 was synthesized stereoselectively with the precursor η(5)-(pentamethyl-cyclopentadienyl) tribenzyloxide titanium (Cp*Ti(OBz)3) and methylaluminoxane (MAO). The effects of polymerization conditions, trime...Polybutene-1 was synthesized stereoselectively with the precursor η(5)-(pentamethyl-cyclopentadienyl) tribenzyloxide titanium (Cp*Ti(OBz)3) and methylaluminoxane (MAO). The effects of polymerization conditions, trimethyl alumina (TMA) content in MAO and temperature on the crystalline and molecular weight of the products, and catalytic activity were investigated. The structural properties of the polybutene-1 were characterized with (13)C NMR and WAXD.展开更多
Deformation-induced phase transition of FormⅡto FormⅠin polybutene-1(PB-1)has been investigated by time-resolved Fourier transform infrared(FTIR)spectroscopy over a wide temperature range from 25℃to 105℃.The initi...Deformation-induced phase transition of FormⅡto FormⅠin polybutene-1(PB-1)has been investigated by time-resolved Fourier transform infrared(FTIR)spectroscopy over a wide temperature range from 25℃to 105℃.The initial film sample containing orientated lamellae is prepared by pre-stretching of PB-1 melt followed by solidification.This is to realize a homogeneity of subsequent deformation at the mesoscale of lamellar stacks by avoiding large-scale spherulites.The deformation induced phase transition is recognized to occur with two stages:first,FormⅡundergoes the lamellar fragmentation,slipping or local melting after yielding to activate its transition to FormⅠ,which may be realized by releasing the restrictions on chains translational movements in crystalline phase;second,the phase transition proceeds with a continuous dissipation of external work and determines the tensile mechanical response of film.To quantify the relationship between crystalline transition of FormⅡto FormⅠand external tensile field,a simple kinetic equation is well established based on FTIR measurement.The equation can describe not only the dependence of crystal transitional degree on applied specific work,but also the retardation effect of elevating temperature on phase transition.展开更多
The effects of weight-average molecular(Mw),molecular weight distribution(MWD),and isotacticity on the linear viscoelastic behavior of polybutene-1 melts are studied.It is observed that the linear viscoelastic region ...The effects of weight-average molecular(Mw),molecular weight distribution(MWD),and isotacticity on the linear viscoelastic behavior of polybutene-1 melts are studied.It is observed that the linear viscoelastic region becomes slightly narrower with increasing frequency.In frequency sweeps,the transition of the polymer melts flow from Newtonian flow to power-law flow can be observed.The melts with higher Mw and:or broader MWD,as well as higher isotacficity exhibit higher complex viscosity,zero shear viscosity,viscoelasticity moduli,relaxation modulus,broader transition zone,while lower critical shear rate,non-Newtonian index,and the frequency at which elasticity begins to play an important role.The relationship of zero shear viscosity on Mw has been established,which agrees with the classical power law.Furthermore,it is found that the cross-over frequency decreases with increasing Mw and the cross-over modulus increases with narrowing MWD.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos. 52173013 and 52373015)。
文摘Polybutene-1(PB-1) is a semi-crystalline polymer with excellent mechanical properties. However, its practical application is significantly hindered by the slow Form Ⅱ-Ⅰ transition, which can take up to several days to complete. While prior research established that long-chain branching(LCB) structures synthesized via ω-alkenylmethyldichlorosilane copolymerization-hydrolysis(ACH) chemistry markedly accelerate this transition, this work demonstrates that H-shaped LCB structures constructed through copolymerization with 1,9-decadiene exhibit the capability to facilitate Form Ⅱ-Ⅰ transition in most systems evaluated herein. However, low branching efficiency concurrently generates extended alkyl pendant chains, which impose pronounced steric-hindrance-driven suppression on the transition kinetics, thereby substantially diminishing the net acceleration effect of the LCB structures, even resulting in a net retardation effect in certain systems. Notably, a significant synergistic acceleration effect emerged between the H-shaped LCB structures and propylene comonomer units. These findings confirm that the H-shaped LCB structures play a role in promoting the Form II-I transformation process, which is independent of the synthetic pathways, thereby providing more strategies for addressing the long-standing processing problems of PB-1.
基金financially supported by the National Natural Science Foundation of China(No.22175183)。
文摘The slow phase transition from formⅡto formⅠhas always been an important factor that restricts the processing and application of polybutene-1(PB-1).After extensive efforts,a set of effective methods for promoting the phase transition rate in PB-1 was established by adjusting the crystallization,nucleation,and growth temperatures.Nevertheless,low-molecular-weight PB-1(LMWPB-1)faces challenges because this method requires a low crystallization temperature,which is difficult to achieve during extrusion processing.In this study,we attempted to increase the phase transition rate in PB-1 by changing the annealing temperature after processing rather than the crystallization temperature in the classical scheme.The results indicated that regardless of low-or high-molecular-weight PB-1,repeated annealing between 0 and 90℃could also promote formⅡto formⅠphase transition.The initial content of formⅠincreased with the heating and cooling cycles.The half-time of the phase transition(t_(1/2))was also shortened after heating/cooling.After 100 heating/cooling cycles,t_(1/2) was reduced to one-quarter of that without annealing,which had almost the same effect as the crystallization temperature at 25℃in promoting the phase transition.This study indicates that annealing after processing is also an important factor affecting the phase transition of PB-1,and should receive sufficient attention.
基金financially supported by the Major Science and Technology Innovation Project of Shandong Province(No.2019JZZY010352)Natural Science Foundation of Shandong Province(ZR2019MB072)Taishan Scholar Program
文摘For the solid-solid transformation from formⅡto formⅠof isotactic polybutene-1(iPB),the temperature dependence of formⅠnucleation and growth was deemed to control the transformation process.However,the relationship between formⅠformation and formⅡdisappearance in the transformation process is not clear.In this work,the spontaneous crystal transformation from formⅡtoⅠof iPB with 81 mol%mmmm sequence concentration is studied firstly by tracking the two processes,the decay of formⅡand the yielding of formⅠin a wide range of temperature spanning from 0℃to 50℃and in a long transformation time ranging from 5 min to 65 days with in situ FTIR and WAXD.Unlike the literature reports,the decay rate of formⅡis firstly found to be lower than the yielding rate of formⅠat all studied temperatures,especially at low transition temperature.This is attributed to the amorphous chains which locate near crystal lamella participating into the nucleation of formⅡ.The regular chain folding and growth of i PB formⅠfrom amorphous chains containing short isotactic sequences also lead to an increase in crystallinity of formⅠcompared with that of initial formⅡcrystallized at 60℃.An increase in the annealing temperature results in decrease in crystallinity and increase in lamellae thickness of i PB formⅠ.
基金financially supported by the National Natural Science Foundation of China (Nos. 51673147, 51573131, and 21374077)
文摘Isotactic polybutene-1 (iPB-1) is a semi-crystalline polymer with polymorph and puzzled structural transitions. The stable form I of iPB-1 with excellent physical and mechanical properties can hardly be obtained directly from the melt;instead, metastable form II will spontaneously and slowly transform into form I. Bypassing the unstable form II formation is of great significance in polymer processing, which inspires extensive research on seeking the pathways to direct formation of form I. Methods for accelerating form II to I transition are another main focus in terms of practical approach for directly obtaining form I. Taking advantage of the solvent, an ultrafast transition of iPB-1 from form II to I within minutes has been achieved at room temperature. Such an ultrafast transition is detected after treating with dichloromethane (DCM) at 30 ℃, though the framework of isothermally crystalized iPB-1 spherulite morphology could not be fully modified. The ultrafast II-I transition of iPB-1 is attributed to the solvent-induced packed-mesophase and temperature-selected chain conformation adjustment.This ultrafast transition would shed light on understanding the mechanisms of polymorphic transitions in iPB-1.
基金financially supported by the Special Foundation of Taishan Mountain Scholar Constructive Programthe National Natural Science Foundation of China(No.21174074)+3 种基金Shandong Provincical Key R&D Program(No.2015GGX102019)Shandong Provincial Natural Science Fund for Distinguished Young Scholars(No.JQ201213)the Nature Science Foundation of Shandong Province(No.ZR2013BM004)the Yellow River Delta Scholar program(Office of National University Science&Technology Park Administrative Committee(China University of Petroleum))
文摘Solvent annealing is a facile method for changing the aggregated microstructure and physical properties of polymer materials.In this paper,we addressed the effects of solvent vapor annealing,including chloroform and water vapor,on the polymorphic transformation in both hot-pressed film and electrospun nonwoven of isotactic polybutene-1(PB-1)by means of in situ Fourier transform infrared spectroscopy(FTIR).The pretty rapid transition rate caused by the increased motion of molecular chains under chloroform vapor is associated with a lowest crystallinity.Also,a decreased crystallinity with the crystal transition occurred in electrospun nonwovens resulting from the relaxation of the stretched molecular chains into amorphous state rather than realignment into crystal form I predominating the crystal transition process.
基金supported by the Major Scientific and Technological Innovation Project of Shandong Province(No.2019JZZY010352)Natural Science Foundation of Shandong Province(No.ZR2019MB072)and Taishan Scholar Program.
文摘The composition and structure of polymer largely determine the properties of its final products.As a novel polymer material,the composition,structure,and properties of the isotactic polypropylene/polybutene-1 in-reactor alloy(PPIPB alloy)synthesized by sequential two-stage polymerization with Ziegler-Natta catalyst were correlated for the first time in this work.The iPP/PB alloy was fractionated by temperature rising elution fractionation(TREF)in a broad temperature ranged from-30℃to 140℃,and the chain microstructures and sequence distributions of isolated fractions were analyzed by DSC,GPC,13C-NMR,and FTIR.The iPP/IPB alloy was composed of five components,namely high isotactic PB(PB,85.8 wt96),medium isotactic PB(mPB,5.1 wt%),polyl(butene-1)-block propylene copolymers(PB-6 PP,4.1 wt%6)which contained PB and PP blocks with dfferent lengths according to the isolation temperature,isotactic PP(iPP,2.7 wt%6),and atactic PB(aPB,2.3 wt96).Compared to other commercial pipe materials,the P/iPB alloy presented outstanding thermal creep resistance and gas permeability resistance,high strength and low deformation at high temperature,and appropriate flexural strength.The roles of PP and PB-b-PP components in the alloy were interpreted.This work is expected to elucidate the potential application of PPIPB aloy as pipe materials and provide solutions for the design and synthesis of high performance pipe materials.
文摘Polybutene-1 was synthesized stereoselectively with the precursor η(5)-(pentamethyl-cyclopentadienyl) tribenzyloxide titanium (Cp*Ti(OBz)3) and methylaluminoxane (MAO). The effects of polymerization conditions, trimethyl alumina (TMA) content in MAO and temperature on the crystalline and molecular weight of the products, and catalytic activity were investigated. The structural properties of the polybutene-1 were characterized with (13)C NMR and WAXD.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51803189,51503186)the Postdoctoral Science Foundation of China(No.2018M630832).
文摘Deformation-induced phase transition of FormⅡto FormⅠin polybutene-1(PB-1)has been investigated by time-resolved Fourier transform infrared(FTIR)spectroscopy over a wide temperature range from 25℃to 105℃.The initial film sample containing orientated lamellae is prepared by pre-stretching of PB-1 melt followed by solidification.This is to realize a homogeneity of subsequent deformation at the mesoscale of lamellar stacks by avoiding large-scale spherulites.The deformation induced phase transition is recognized to occur with two stages:first,FormⅡundergoes the lamellar fragmentation,slipping or local melting after yielding to activate its transition to FormⅠ,which may be realized by releasing the restrictions on chains translational movements in crystalline phase;second,the phase transition proceeds with a continuous dissipation of external work and determines the tensile mechanical response of film.To quantify the relationship between crystalline transition of FormⅡto FormⅠand external tensile field,a simple kinetic equation is well established based on FTIR measurement.The equation can describe not only the dependence of crystal transitional degree on applied specific work,but also the retardation effect of elevating temperature on phase transition.
基金financially supported by the National Basic Research Program of China(No.2015CB654700(2015CB654706))Special Foundation of Taishan Mountain Scholar Constructive Program+5 种基金National Key Technology R&D Program of China(No.2011BAE26B05)Shandong Provincial Natural Science Fund for Distinguished Young Scholars(No.JQ201213)the National Natural Science Foundation of China(No.21174074)the Nature Science Foundation of Shandong Province(No.ZR2013BM004)Shandong province science and technology development plan(2012GGA05042)support from the Yellow River Delta Scholar program Office of National University Science&Technology Park Administrative Committee(China University of Petroleum)
文摘The effects of weight-average molecular(Mw),molecular weight distribution(MWD),and isotacticity on the linear viscoelastic behavior of polybutene-1 melts are studied.It is observed that the linear viscoelastic region becomes slightly narrower with increasing frequency.In frequency sweeps,the transition of the polymer melts flow from Newtonian flow to power-law flow can be observed.The melts with higher Mw and:or broader MWD,as well as higher isotacficity exhibit higher complex viscosity,zero shear viscosity,viscoelasticity moduli,relaxation modulus,broader transition zone,while lower critical shear rate,non-Newtonian index,and the frequency at which elasticity begins to play an important role.The relationship of zero shear viscosity on Mw has been established,which agrees with the classical power law.Furthermore,it is found that the cross-over frequency decreases with increasing Mw and the cross-over modulus increases with narrowing MWD.
