The melts of a series of low molecular weight poly（ethylene oxide）（PEO） fractions on mica surfaces were studied by atomic force microscopy（AFM） and X-ray reflectivity（XRR） measurement.The PEO ultrathin films w...The melts of a series of low molecular weight poly（ethylene oxide）（PEO） fractions on mica surfaces were studied by atomic force microscopy（AFM） and X-ray reflectivity（XRR） measurement.The PEO ultrathin films were obtained via static dilute solution casting.Different from the melts of the PEO with both methoxyl（（—OCH3）） end groups that are dewetted on the mica surface,a pseudo-dewetting phenomenon of the PEO melts was observed when either one end group of the PEOs becomes hydroxyl（—OH） or both are hydroxyl groups.The wetting layer thicknesses of the pseudo-dewetted melts were measured to be 4.5～4.7 nm,independent on the molecular weight and the end groups of PEOs.However,the PEO melt droplets on the wetting layer varied from spherical caps with relatively high contact angle to irregular shapes with relatively low contact angle when increasing the molecular weight and the hydrophobicity of end groups of PEOs.展开更多
Discrete nano-aggregates of a poly(ethylene oxide)-b-polybutadiene diblock copolymer (PEO-b-PB) were obtained by self-assembling of the copolymer in a selective solvent of PB followed by the shell cross-linking.The av...Discrete nano-aggregates of a poly(ethylene oxide)-b-polybutadiene diblock copolymer (PEO-b-PB) were obtained by self-assembling of the copolymer in a selective solvent of PB followed by the shell cross-linking.The average behaviors of the PEO crystallization and melting confined within the nano-structured aggregates were studied by differential scanning calorimetry experiments.The experiments demonstrated that the confinement effect arisen from the shells could be tuned by adjusting the degree of PB cross-linking.For the deeply cross-linked sample,the individual particles only crystallized at very low crystallization temperature (T c),wherein the homogenous primary nucleation determined the crystallization rate.For the lightly cross-linked sample,the confinement effect is T c dependent.When T c exceeded 42℃,the lightly cross-linked sample possessed a higher melting temperature and a lower crystallinity compared with the pure PEO-b-PB.展开更多
A series of newly designed monomers of 2-vinylterephthalates (VT) were synthesized. The monomers contain onephenylene group connected with two alkyl groups (carbon number varying from 1 to 6) via ester linkage. Their ...A series of newly designed monomers of 2-vinylterephthalates (VT) were synthesized. The monomers contain onephenylene group connected with two alkyl groups (carbon number varying from 1 to 6) via ester linkage. Their chemicalstructures were confirmed by mass spectroscopy (MS), ~1-H-NMR, and elemental analysis (EA). The corresponding polymers,poly[di(alkyl) vinylterephthalate]s (PDAVTs), were obtained using convenional free redical polymerization. The polymerswere found to be able to develop inio liquid crystalline phase when the size of the alkyl group in the side-chain increases tobe larger than the ethyl group.展开更多
文摘The melts of a series of low molecular weight poly（ethylene oxide）（PEO） fractions on mica surfaces were studied by atomic force microscopy（AFM） and X-ray reflectivity（XRR） measurement.The PEO ultrathin films were obtained via static dilute solution casting.Different from the melts of the PEO with both methoxyl（（—OCH3）） end groups that are dewetted on the mica surface,a pseudo-dewetting phenomenon of the PEO melts was observed when either one end group of the PEOs becomes hydroxyl（—OH） or both are hydroxyl groups.The wetting layer thicknesses of the pseudo-dewetted melts were measured to be 4.5～4.7 nm,independent on the molecular weight and the end groups of PEOs.However,the PEO melt droplets on the wetting layer varied from spherical caps with relatively high contact angle to irregular shapes with relatively low contact angle when increasing the molecular weight and the hydrophobicity of end groups of PEOs.
基金supported by the National Natural Science Foundation of China (20129001)the Research Grants Council of Hong Kong, China(CA05/06.SC02)R/D Fund of Shenzhen University, China (200824)~~
文摘Discrete nano-aggregates of a poly(ethylene oxide)-b-polybutadiene diblock copolymer (PEO-b-PB) were obtained by self-assembling of the copolymer in a selective solvent of PB followed by the shell cross-linking.The average behaviors of the PEO crystallization and melting confined within the nano-structured aggregates were studied by differential scanning calorimetry experiments.The experiments demonstrated that the confinement effect arisen from the shells could be tuned by adjusting the degree of PB cross-linking.For the deeply cross-linked sample,the individual particles only crystallized at very low crystallization temperature (T c),wherein the homogenous primary nucleation determined the crystallization rate.For the lightly cross-linked sample,the confinement effect is T c dependent.When T c exceeded 42℃,the lightly cross-linked sample possessed a higher melting temperature and a lower crystallinity compared with the pure PEO-b-PB.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 20134010 and No. 20025414).
文摘A series of newly designed monomers of 2-vinylterephthalates (VT) were synthesized. The monomers contain onephenylene group connected with two alkyl groups (carbon number varying from 1 to 6) via ester linkage. Their chemicalstructures were confirmed by mass spectroscopy (MS), ~1-H-NMR, and elemental analysis (EA). The corresponding polymers,poly[di(alkyl) vinylterephthalate]s (PDAVTs), were obtained using convenional free redical polymerization. The polymerswere found to be able to develop inio liquid crystalline phase when the size of the alkyl group in the side-chain increases tobe larger than the ethyl group.
