In this study, recovery processes of isotactic polypropylene （iPP） melted spherulites at 135 ℃ after melting at higher temperatures （170 ℃-176 ℃） were investigated with polarized optical microscopy and Fourier ...In this study, recovery processes of isotactic polypropylene （iPP） melted spherulites at 135 ℃ after melting at higher temperatures （170 ℃-176 ℃） were investigated with polarized optical microscopy and Fourier transform infrared spectroscopy. The recovery temperature was fixed to exclude the interference from heterogeneous nuclei. After melting at temperatures between 170 ℃ and 174 ℃, the melted spherulite could recover back to the origin spberulite at low temperatures. Interestingly, a distinct infrared spectrum from iPP melt and crystal was observed in the early stage of recovery process after melting at low temperatures, where only IR bands resulting from short helices with 12 monomers or less can be seen, which indicates that the presence of crystal residues is not the necessary condition for the polymer memory effect. Avrami analysis further indicated that crystallization mainly took place in melted lamellae. After melting at higher temperatures, melted spherulite cannot recover. Based on above findings, it is proposed that the memory effect can be mainly ascribed to melted lamellae, during which crystalline order is lost but conformational order still exists. These conformational ordered segments formed aggregates, which can play as nucleation precursors at low temperatures.展开更多
Developing organic room-temperature phosphorescence(RTP)materials with a wide range of tunable-emission is significant in expanding the applications of RTP materials.Herein,we rationally designed amphiphilic alternati...Developing organic room-temperature phosphorescence(RTP)materials with a wide range of tunable-emission is significant in expanding the applications of RTP materials.Herein,we rationally designed amphiphilic alternating copolymers poly(1,2-bis(4-alkoxyphenyl)ethane-1,2-dione-alt-(ethylene glycol)x)(P(Bz-alt-EGx))that combined the advantage of alternating benzil and EGxskeleton,and tunable mainchain conformation.Through a mainchain conformation ordering assembly(COA)process,P(Bz-alt-EGx)self-assembled into well-defined platelets,and such assemblies emitted blue RTP at ca.425 nm due to the ordered folded-chain conformation and confined microenvironment.In contrast,traditional self-assembly(TA)of P(Bz-alt-EGx)obtained less ordered aggregates,such as asymmetric worms,vesicles,and rod-like micelles.The resultant less ordered aggregates exhibited yellow-green RTP at ca.550 nm.The wide-tuning RTP emission in solution(between blue and yellow-green,over125 nm)is realized using the P(Bz-alt-EG_(x))alternating copolymers under the treatment of different self-assembly conditions.This study uncovers a new strategy to tailor the RTP emission through different self-assembly pathways and holds great promise for the fabrication of advanced optical materials.展开更多
Surfactants tend to adsorb on the surface/interface mostly in a directional manner.The alkyl chain orientation and conformation order for molecular monolayers of sodium dodecylbenzenesulfonate(SDBS)at low concentratio...Surfactants tend to adsorb on the surface/interface mostly in a directional manner.The alkyl chain orientation and conformation order for molecular monolayers of sodium dodecylbenzenesulfonate(SDBS)at low concentrations are studied by using the sum frequency generation vibrational spectroscopy(SFG-VS).The molecular arrangement of the surfactants adsorbed at the solid/liquid interface is further investigated.It is found that the arrangement of the SDBS at the interface becomes relatively ordered with increasing bulk concentration.Meanwhile,the orientation angle reduces gradually,and the molecules tend to be upright state.In addition,the effect of friction on the conformation order and orientation angle are also analyzed.The intensity of the SDBS vibrational contraction peak becomes lower after friction,which indicates that the anion has a reorientation process at the interface.The arrangement of molecules becomes more disordered due to friction.The orientation angle increases slightly,which indicates the monolayer has an inclined trend relative to the lateral direction on the interface.A modified adsorption model considering friction effect is proposed.This work may provide a reference for the further study of adsorption mechanism and application of surfactants.展开更多
基金financially supported by the China Postdoctoral Science Foundation(No.2012M521233)the Fundamental Research Funds for the Central Universities(WK2310000031)+3 种基金the National Natural Science Foundation of China(Nos.51033004,51227801,51303166)National Natural Science Funds for Distinguished Young Scholars(No.51325301)the 973 program of MOST(2010CB934504)supported by the Opening Project of Soochow University Biomedical Polymers Laboratory and the Jiangsu Key Laboratory of Advanced Functional Polymer Design and Application(Soochow University)
文摘In this study, recovery processes of isotactic polypropylene （iPP） melted spherulites at 135 ℃ after melting at higher temperatures （170 ℃-176 ℃） were investigated with polarized optical microscopy and Fourier transform infrared spectroscopy. The recovery temperature was fixed to exclude the interference from heterogeneous nuclei. After melting at temperatures between 170 ℃ and 174 ℃, the melted spherulite could recover back to the origin spberulite at low temperatures. Interestingly, a distinct infrared spectrum from iPP melt and crystal was observed in the early stage of recovery process after melting at low temperatures, where only IR bands resulting from short helices with 12 monomers or less can be seen, which indicates that the presence of crystal residues is not the necessary condition for the polymer memory effect. Avrami analysis further indicated that crystallization mainly took place in melted lamellae. After melting at higher temperatures, melted spherulite cannot recover. Based on above findings, it is proposed that the memory effect can be mainly ascribed to melted lamellae, during which crystalline order is lost but conformational order still exists. These conformational ordered segments formed aggregates, which can play as nucleation precursors at low temperatures.
基金supported by the National Natural Science Foundation of China(52073094,52273291,52273008)the Shanghai Scientific and Technological Innovation Project(22ZR1479300)the Shanghai Rising-Star Program(23QA1402500)。
文摘Developing organic room-temperature phosphorescence(RTP)materials with a wide range of tunable-emission is significant in expanding the applications of RTP materials.Herein,we rationally designed amphiphilic alternating copolymers poly(1,2-bis(4-alkoxyphenyl)ethane-1,2-dione-alt-(ethylene glycol)x)(P(Bz-alt-EGx))that combined the advantage of alternating benzil and EGxskeleton,and tunable mainchain conformation.Through a mainchain conformation ordering assembly(COA)process,P(Bz-alt-EGx)self-assembled into well-defined platelets,and such assemblies emitted blue RTP at ca.425 nm due to the ordered folded-chain conformation and confined microenvironment.In contrast,traditional self-assembly(TA)of P(Bz-alt-EGx)obtained less ordered aggregates,such as asymmetric worms,vesicles,and rod-like micelles.The resultant less ordered aggregates exhibited yellow-green RTP at ca.550 nm.The wide-tuning RTP emission in solution(between blue and yellow-green,over125 nm)is realized using the P(Bz-alt-EG_(x))alternating copolymers under the treatment of different self-assembly conditions.This study uncovers a new strategy to tailor the RTP emission through different self-assembly pathways and holds great promise for the fabrication of advanced optical materials.
基金The work was financially supported by the National Natural Science Foundation of China(Nos.51675297 and 51527901).
文摘Surfactants tend to adsorb on the surface/interface mostly in a directional manner.The alkyl chain orientation and conformation order for molecular monolayers of sodium dodecylbenzenesulfonate(SDBS)at low concentrations are studied by using the sum frequency generation vibrational spectroscopy(SFG-VS).The molecular arrangement of the surfactants adsorbed at the solid/liquid interface is further investigated.It is found that the arrangement of the SDBS at the interface becomes relatively ordered with increasing bulk concentration.Meanwhile,the orientation angle reduces gradually,and the molecules tend to be upright state.In addition,the effect of friction on the conformation order and orientation angle are also analyzed.The intensity of the SDBS vibrational contraction peak becomes lower after friction,which indicates that the anion has a reorientation process at the interface.The arrangement of molecules becomes more disordered due to friction.The orientation angle increases slightly,which indicates the monolayer has an inclined trend relative to the lateral direction on the interface.A modified adsorption model considering friction effect is proposed.This work may provide a reference for the further study of adsorption mechanism and application of surfactants.
