查看更多>>摘要：For the first time,a highly crystalline porous shish-kebab structure with a high degree of crystallinity was obtained by using a combination of two methods for the formation of porous polymeric materials.A treatment procedure using supercritical carbon dioxide(scCO2)was carried out for oriented ultrahigh molecular weight polyethylene(UHMWPE)films,which provided special conditions for the crystallization of dissolved UHMWPE macromolecules on the surface of oriented UHMWPE crystals.The prepared porous materials were investigated by scanning electron microscopy(SEM)and differential scanning calorimetry(DSC).The particularity of the obtained porous shish-kebab is the absence of the amorphous phase between lamellar crystals(kebabs).The obtained pores had an oval shape,and they were oriented in the orientation direction of the UHMWPE macromolecules.The pore size ranged from 0.05 μm to 4 μm.Controlling the conditions for the crystallization of the UHMWPE macromolecules using supercritical CO2 gives the possibility to control the size of both lamellar disks and pores formed.
查看更多>>摘要：Poly(3,4-ethylenedioxythiophene)(PEDOT)is one of the most successful conductive polymers that recently has been used in wearable sensors for human health monitoring.In this work,we prepared a series of PEDOT hybrids consisting of PEDOT,sodium poly(styrene sulfonate)(PSSNa)and polyethylene oxide(PEO),and their preparation could be scaled-up via an adapted solid-state polymerization process.The resistance of the as-prepared PEDOT:PSS/PEO hybrid shows clear temperature response,i.e.,it decreases almost linearly with the temperature increase.To understand this phenomenon,the in situ synchrotron radiation wide-and small-angle X-ray scattering(WAXS/SAXS)characterizations were undertaken to study the temperature-dependent microstructure change of the PEDOT:PSS/PEO hybrid.It demonstrated that PEDOT formed conductive paths in the hybrids,which were not destroyed by the PEO crystallization.As temperature increased,the PEO crystals'melting and the accompanying reorganization of PEDOT chains endowed the hybrid sample temperature responsiveness.Based on these fundamental knowledges,the hybrid materials were used to fabricate flexible wearable sensor that showing temperature sensing performance with an accuracy of 1 ℃.These findings shed lights on the scalable manufacturing of wearable sensors for body temperature monitoring.
查看更多>>摘要：The chain dynamics heterogeneity of the poly(vinyl butyral)(PVB)plasticized by triethylene glycol bis(2-ethylhexanoate)(TEG-EH)was investigated by various solid-state NMR techniques.The plasticized PVB shows two domains in distinct molecular dynamics differences,namely,rigid and soft domains,where the latter is the plasticizer-rich domain.The time domain low field NMR was first used to investigate the dynamics heterogeneity of the plasticized PVB,and the results show the decreasing activated energy of components in the soft domain of plasticized PVB(Ea=20.2 kJ/mol)as compared with that of the pristine one(Ea=24.3 kJ/mol).Detailed dynamics heterogeneity was obtained by high-field NMR with site-specific features.The quadrupole-echo 2H-NMR was adopted to elucidate the dynamics heterogeneity of the vinyl alcohol(VA)units,where only the hydroxyl group of VA is deuterated.The 1H-13C WISE NMR spectra show that there is not much difference in the mobility of the VB unit in PVB with and without plasticizer,whereas the glass transition temperature differed by approximately 53 ℃.This is further supported by Torchia's T1 relaxation measurements.The origin of such an unusual phenomenon is attributed to the critical role of the remaining VA(～22％)in the soft domain,where the VA units locally aggregate through hydrogen bonding.Also,the existence of a mobility gradient in the VB unit has been demonstrated.Moreover,the mobility difference for VB with different stereo-geometry(meso or racemic conformation)is observed for the first time.This indicates the importance of modulating the ratio of meso over racemic VB for controlling the macroscopic performance of PVB.
查看更多>>摘要：The polymer translocation through a nanopore from a donor space(or named cis side)to a receiver space(trans side)in the chaperone-induced crowded environment has attracted increasing attention in recent years due to its significance in biological systems and technological applications.In this work,we mainly focus on the effects of chaperone concentration and chaperone-polymer interaction on the polymer translocation.By assuming the polymer translocation to be a quasi-equilibrium process,the free energy F of the polymer can be estimated by Rosenbluth-Rosenbluth method and then the translocation time r can be calculated by Fokker-Plank equation based on the obtained free energy landscape.Our calculation results show that the translocation time can be controlled by independently tuning the chaperone concentration and chaperone-polymer interaction at the cis side or the trans side.There exists a critical chaperone-polymer attractionε*=-0.2 at which the volume exclusion and interaction effects of the chaperone can balance each other.Additionally,we also find that at large chaperone-polymer attraction,the translocation time is mainly governed by the diffusion coefficient of the polymer.
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