Surface molecular motions of amorphous polymeric solids have been directly measured on the basis of scanningviscoelasticity microscopic(SVM)and lateral force microscopic(LFM)measurements.SVM and LFM measurements werec...Surface molecular motions of amorphous polymeric solids have been directly measured on the basis of scanningviscoelasticity microscopic(SVM)and lateral force microscopic(LFM)measurements.SVM and LFM measurements werecarried out for films of conventional monodisperse polystyrene(PS)with sec-butyl and proton-terminated end groups atroom temperature.In the case of the number-average molecular weight,M_(n),less than ca.4.0×10^(4),the surface was in a glass-rubber transition state even though the bulk glass transition temperature,T_(g)was far above room temperature,meaning thatthe surface molecular motion was fairly active compared with that in the bulk.LFM measurements of the,monodisperse PSfilms at various scanning rates and temperatures revealed that the time-temperature superposition was applicable to thesurface mechanical relaxation behavior and also that the surface glass transition temperature,T_(g)^(σ),was depressed incomparison with the bulk one even though the magnitude of M_n was fairly high at 1.40×10~5.The surface molecular motionof monodisperse PS with various chain end groups was investigated on the basis of temperature-dependent scanningviscoelasticity microscopy(TDSVM).The T_(g)^(σ)s for the PS films with M_n of 4.9×10^(6)to 1.45×10^(6)measured by TDSVMwere smaller than those for the bulk one,with corresponding M_ns,and the T_(g)^(σ)s for M_ns smaller than ca.4.0×10^(4)were lowerthan room temperature(293 K).The active thermal molecular motion at the polymeric solid surface can be interpreted interms of an excess free volume near the surface region induced by the surface localization of chain end groups.In the case ofM_n=ca.5.0×10^(4),the T_(g)^(σ)s for theα,ω-diamino-terminated PS(α,ω-PS(NH_2)_2)andα,ω-dicarboxy-terminated PS(α,ω-PS(COOH)_2)films were higher than that of the PS film.The change of T_(g)^(σ)for the PS film with various chain end groups canbe explained in terms of the depth distribution of chain end groups at the surface region depending on the relativehydrophobicity.展开更多
Olympus sponsors the first national confocal microscopic-image competition The Olympus Cup National Confocal Microscopic-image Competition, the first of its kind in China,lifted its curtain in Beijing on November 1. O...Olympus sponsors the first national confocal microscopic-image competition The Olympus Cup National Confocal Microscopic-image Competition, the first of its kind in China,lifted its curtain in Beijing on November 1. Olympus (China) Co. Ltd. is the competition’s sole spon-展开更多
基金This work was supported in part by a Grant-in-Aid for COE Research"Design and Control of Advanced Molecular Assembly Systems"from the Ministry of Fducation Science Sports and Culture Japan(408CE2005).
文摘Surface molecular motions of amorphous polymeric solids have been directly measured on the basis of scanningviscoelasticity microscopic(SVM)and lateral force microscopic(LFM)measurements.SVM and LFM measurements werecarried out for films of conventional monodisperse polystyrene(PS)with sec-butyl and proton-terminated end groups atroom temperature.In the case of the number-average molecular weight,M_(n),less than ca.4.0×10^(4),the surface was in a glass-rubber transition state even though the bulk glass transition temperature,T_(g)was far above room temperature,meaning thatthe surface molecular motion was fairly active compared with that in the bulk.LFM measurements of the,monodisperse PSfilms at various scanning rates and temperatures revealed that the time-temperature superposition was applicable to thesurface mechanical relaxation behavior and also that the surface glass transition temperature,T_(g)^(σ),was depressed incomparison with the bulk one even though the magnitude of M_n was fairly high at 1.40×10~5.The surface molecular motionof monodisperse PS with various chain end groups was investigated on the basis of temperature-dependent scanningviscoelasticity microscopy(TDSVM).The T_(g)^(σ)s for the PS films with M_n of 4.9×10^(6)to 1.45×10^(6)measured by TDSVMwere smaller than those for the bulk one,with corresponding M_ns,and the T_(g)^(σ)s for M_ns smaller than ca.4.0×10^(4)were lowerthan room temperature(293 K).The active thermal molecular motion at the polymeric solid surface can be interpreted interms of an excess free volume near the surface region induced by the surface localization of chain end groups.In the case ofM_n=ca.5.0×10^(4),the T_(g)^(σ)s for theα,ω-diamino-terminated PS(α,ω-PS(NH_2)_2)andα,ω-dicarboxy-terminated PS(α,ω-PS(COOH)_2)films were higher than that of the PS film.The change of T_(g)^(σ)for the PS film with various chain end groups canbe explained in terms of the depth distribution of chain end groups at the surface region depending on the relativehydrophobicity.
文摘Olympus sponsors the first national confocal microscopic-image competition The Olympus Cup National Confocal Microscopic-image Competition, the first of its kind in China,lifted its curtain in Beijing on November 1. Olympus (China) Co. Ltd. is the competition’s sole spon-
