The degradation mechanism of photocrosslinking products formed by cyclized polyisoprene-diazide system under the influence of the different alkyl benzene sulfonic acids was studied. The effects of alkyl chain length a...The degradation mechanism of photocrosslinking products formed by cyclized polyisoprene-diazide system under the influence of the different alkyl benzene sulfonic acids was studied. The effects of alkyl chain length and the concentration of alkyl benzene sulfonic acids on the rate of degradation reaction were discussed. It was found that in the initial stage of degradation, the cyclicity ratio and the average fused ring number did not change considerably, but the percentage of uncyclized parts content varied significantly. The suitable mechanism was supposed.展开更多
This paper reports that the pattern formation in homogeneous solutions of polyisoprene in toluene saturated with C60 induced by a continuous-wave visible laser is observed experimentally. The transmitted beam patterns...This paper reports that the pattern formation in homogeneous solutions of polyisoprene in toluene saturated with C60 induced by a continuous-wave visible laser is observed experimentally. The transmitted beam patterns change with the increase of the laser irradiation time. In the initial phase, the patterns with concentric ring-shaped structure are formed. In the end, the patterns become speckle-shaped. The incubation time of the transmitted beam widening is inversely proportional to the laser power density and solution concentration. The pattern formation results from the optical-field-induced refractive index changes in the solutions, but the mechanism of optical-field-induced refractive index changes in the polymer solutions needs to be further studied.展开更多
The epoxidation of polydienes yields materials with improved properties, which can be tuned by the control of the epoxidation degree. In this work, we retake a known process, the epoxidation of polyisoprene, by a diff...The epoxidation of polydienes yields materials with improved properties, which can be tuned by the control of the epoxidation degree. In this work, we retake a known process, the epoxidation of polyisoprene, by a different approach, in which the quantification of parameters influencing the epoxidation, such as temperature, oxidant and catalyst concentration, and reaction time degree is evaluated. We measured the influence of each parameter, allowing anyone who aims a polymer with a certain degree of epoxidation to choose which conditions are best suitable for reaching his goal.展开更多
In the paper,the structures of the crystalline 3,4-polyisoprene(3,4-PI) which was first synthesized in our institute,were investigated by using Wide Angle X-ray Diffraction(WAXD);Small Angle X-ray Scattering(SAXS)and ...In the paper,the structures of the crystalline 3,4-polyisoprene(3,4-PI) which was first synthesized in our institute,were investigated by using Wide Angle X-ray Diffraction(WAXD);Small Angle X-ray Scattering(SAXS)and Laue photography in various polymerization conditions and elongate ratios.It was found that reducing reaction velocity was favourable for crystalline capacity.The polymeric structures were dependent mainly on nitrogen electron donor.The degree of crystallinity and long period were increased with elongate ratio,but crystalline size was decreased.The polymers used in the work belong to inhomogeneous particulate system.The particulate radii were between 35-164A.展开更多
For decades,the preparation of polyisoprene rubber that can match the comprehensive properties of natural rubber(NR)has been pursued.While sacrificial bonds have been used to promote the strength and toughness of rubb...For decades,the preparation of polyisoprene rubber that can match the comprehensive properties of natural rubber(NR)has been pursued.While sacrificial bonds have been used to promote the strength and toughness of rubbers,little is known about their effects on fatigue resistance,which is important in dynamic environments.Herein,terminal block and randomly functionalized polyisoprene rubbers tethered with di-alanine,tri-alanine and tetra-alanine were prepared.The results showed that the flow activation energy,aggregates ordering and energy dissipation of the hydrogen-bonded aggregates increase with the elongation of oligopeptide length(XA,X=2,3,4),therefore resulting in enhanced mechanical strength and toughness of corresponding samples.Comparably,the tear strengths are barely affected by oligopeptide lengths in block samples,but promoted from dipeptide to tetrapeptide in random samples,probably due to the well dispersed oligopeptide aggregates.Most importantly,it is found that the tight binding aggregates of oligopeptides are critical for the excellent fatigue resistance,which is absent in polyisoprene and natural rubber.The loose aggregates dissociate and recombine repeatedly under cyclic loading and the tight aggregates keep the network integrated and robust.Interestingly,the largest hysteresis of PIP-4A-V with the longest oligopeptide length give the lowest heat generation,which is contrary to the traditional sacrificial bonds.Overall,the oligopeptide aggregates have repeatable energy dissipation properties and cycle life comparable to or even surpassing those of the linked proteins in NR,resulting in similar tensile strength,fracture toughness,and better fatigue resistance relative to NR.This deep insight on the role of oligopeptide aggregates is very useful for the engineering rubbers served in dynamic environments.展开更多
Through neodymium-mediated coordinative chain transfer copolymerizaiton(CCTcoP),polyisoprenes bearing dual hydroxylated mini-blocky chain-ends were prepared via a three-step strategy.Kinetic studies revealed that,the ...Through neodymium-mediated coordinative chain transfer copolymerizaiton(CCTcoP),polyisoprenes bearing dual hydroxylated mini-blocky chain-ends were prepared via a three-step strategy.Kinetic studies revealed that,the polymerization demonstrated typical features of CCTcoP across the whole polymerization process,i.e.,quasi-living polymerization characteristic,tunable molecular weights,narrow molecular weight distributions,and atom economies.Comparing to previously reported CCTP homopolymerization systems,the presence of oxygen-containing IpOAl polar comonomer slowed down chain transfer rates obviously,rendering slightly higher molecular weights of the resultant PIps and smaller Np(number of polymer chains per Nd atom)values.Moreover,to mimic the structure of natural rubber,the hydroxyl end groups can be facilely modified into phosphonate,amide,and UPy,whose structures were further confirmed by NMR spectra.Incorporation these functionalities could greatly improve the hydrophilic properties of the polymers,as revealed from the significantly reduced static water contact angles.展开更多
文摘The degradation mechanism of photocrosslinking products formed by cyclized polyisoprene-diazide system under the influence of the different alkyl benzene sulfonic acids was studied. The effects of alkyl chain length and the concentration of alkyl benzene sulfonic acids on the rate of degradation reaction were discussed. It was found that in the initial stage of degradation, the cyclicity ratio and the average fused ring number did not change considerably, but the percentage of uncyclized parts content varied significantly. The suitable mechanism was supposed.
基金Project supported by the Multidiscipline Scientific Research Foundation of Harbin Institute of Technology (Grand No HIT. MD. 2003. 08) and the Program of Excellence Team in Harbin Institute of Technology
文摘This paper reports that the pattern formation in homogeneous solutions of polyisoprene in toluene saturated with C60 induced by a continuous-wave visible laser is observed experimentally. The transmitted beam patterns change with the increase of the laser irradiation time. In the initial phase, the patterns with concentric ring-shaped structure are formed. In the end, the patterns become speckle-shaped. The incubation time of the transmitted beam widening is inversely proportional to the laser power density and solution concentration. The pattern formation results from the optical-field-induced refractive index changes in the solutions, but the mechanism of optical-field-induced refractive index changes in the polymer solutions needs to be further studied.
文摘The epoxidation of polydienes yields materials with improved properties, which can be tuned by the control of the epoxidation degree. In this work, we retake a known process, the epoxidation of polyisoprene, by a different approach, in which the quantification of parameters influencing the epoxidation, such as temperature, oxidant and catalyst concentration, and reaction time degree is evaluated. We measured the influence of each parameter, allowing anyone who aims a polymer with a certain degree of epoxidation to choose which conditions are best suitable for reaching his goal.
文摘In the paper,the structures of the crystalline 3,4-polyisoprene(3,4-PI) which was first synthesized in our institute,were investigated by using Wide Angle X-ray Diffraction(WAXD);Small Angle X-ray Scattering(SAXS)and Laue photography in various polymerization conditions and elongate ratios.It was found that reducing reaction velocity was favourable for crystalline capacity.The polymeric structures were dependent mainly on nitrogen electron donor.The degree of crystallinity and long period were increased with elongate ratio,but crystalline size was decreased.The polymers used in the work belong to inhomogeneous particulate system.The particulate radii were between 35-164A.
基金financially supported by the National Natural Science Foundation of China(No.51973126)the State Key Laboratory of Polymer Materials Engineering(No.sklpme20222-11)。
文摘For decades,the preparation of polyisoprene rubber that can match the comprehensive properties of natural rubber(NR)has been pursued.While sacrificial bonds have been used to promote the strength and toughness of rubbers,little is known about their effects on fatigue resistance,which is important in dynamic environments.Herein,terminal block and randomly functionalized polyisoprene rubbers tethered with di-alanine,tri-alanine and tetra-alanine were prepared.The results showed that the flow activation energy,aggregates ordering and energy dissipation of the hydrogen-bonded aggregates increase with the elongation of oligopeptide length(XA,X=2,3,4),therefore resulting in enhanced mechanical strength and toughness of corresponding samples.Comparably,the tear strengths are barely affected by oligopeptide lengths in block samples,but promoted from dipeptide to tetrapeptide in random samples,probably due to the well dispersed oligopeptide aggregates.Most importantly,it is found that the tight binding aggregates of oligopeptides are critical for the excellent fatigue resistance,which is absent in polyisoprene and natural rubber.The loose aggregates dissociate and recombine repeatedly under cyclic loading and the tight aggregates keep the network integrated and robust.Interestingly,the largest hysteresis of PIP-4A-V with the longest oligopeptide length give the lowest heat generation,which is contrary to the traditional sacrificial bonds.Overall,the oligopeptide aggregates have repeatable energy dissipation properties and cycle life comparable to or even surpassing those of the linked proteins in NR,resulting in similar tensile strength,fracture toughness,and better fatigue resistance relative to NR.This deep insight on the role of oligopeptide aggregates is very useful for the engineering rubbers served in dynamic environments.
基金financially supported by the National Natural Science Foundation of China(No.U1862206)Jilin Province Department of Education(No.JJKH20200665KJ)+3 种基金Dr.W.Zhao thanks for the financial support from China Postdoctoral Science Foundation(No.2021M701818)Shandong Provincial Natural Science Foundation,China(No.ZR2022QE237)Qingdao Postdoctoral Applied Research Project,PetroChina Company Limited(No.2020B-2711)H.Liu sincerely acknowledges the financial support from the Taishan Scholars Program。
文摘Through neodymium-mediated coordinative chain transfer copolymerizaiton(CCTcoP),polyisoprenes bearing dual hydroxylated mini-blocky chain-ends were prepared via a three-step strategy.Kinetic studies revealed that,the polymerization demonstrated typical features of CCTcoP across the whole polymerization process,i.e.,quasi-living polymerization characteristic,tunable molecular weights,narrow molecular weight distributions,and atom economies.Comparing to previously reported CCTP homopolymerization systems,the presence of oxygen-containing IpOAl polar comonomer slowed down chain transfer rates obviously,rendering slightly higher molecular weights of the resultant PIps and smaller Np(number of polymer chains per Nd atom)values.Moreover,to mimic the structure of natural rubber,the hydroxyl end groups can be facilely modified into phosphonate,amide,and UPy,whose structures were further confirmed by NMR spectra.Incorporation these functionalities could greatly improve the hydrophilic properties of the polymers,as revealed from the significantly reduced static water contact angles.
