Based on the model of random walk on the simple cubic lattice,the distribution function of conformation of a polymer chain in an interfacial layer was deduced.If the model chain was consisted of N segments, it was pos...Based on the model of random walk on the simple cubic lattice,the distribution function of conformation of a polymer chain in an interfacial layer was deduced.If the model chain was consisted of N segments, it was possible to form both the tail chain, when the terminal segments were adsorbed at the interface, and the adsorbed chain with the non\|terminal group.The conformational number Ω tail of a tail chain is equal to Ω free /(6π N ) 1/2 ,where Ω free is the conformational number of a chain in free state and equals to 6 N for this random walk model. It was found from theoretical analysis that, for the set of a chain attached non\|terminally to the interface, the total conformational number Ω tot is equal to Ω free /6.As an result,the average conformational number m for the chain attached non\|terminally to the interface is Ω \{free\}/6 N .In the case of short chain,for instance N is equal to about 10,the conformational number Ω \{tail\} of tail chain is even larger than the total number Ω \{tot\}. In the limitation of long chain, however, the conformational number Ω \{tail\} for tail chain is nuch large than m,but smaller than Ω \{tot\}. The conclusion is that the distribution function of conformation for chains in the interfacial layer is not uniform,but has a special distribution form described in this paper.展开更多
Five samples of perfluoroheptyl end capped polyacrylic acid ( F P A A) having ahigh surface activity were prepared by free radicalpolymerization ofacrylicacid . Theinitiatorwas perfluorooctanoyl peroxide which produce...Five samples of perfluoroheptyl end capped polyacrylic acid ( F P A A) having ahigh surface activity were prepared by free radicalpolymerization ofacrylicacid . Theinitiatorwas perfluorooctanoyl peroxide which produced the free radicalof heptyl at 45 ℃. The yieldsof F P A A were in the range of 10 % to 25 % . The weight average molecular weights were2 62 ×104 to 7 99 ×104 and the polydispersity indexes were 1 97 to 5 64 ,depending on theconcentration of the initiator in the monomer. The surface tension was about 15m N/m at30 ℃forthe aqueous solution of F P A Awith the weight average molecular weight2 62 ×104in the concentration of about 0 01g/ m L. The molecular areas of F P A A at the air waterinterface under the condition ofcritical micelle concentration were 3 2 to 4 6n m2 ,which areobviously larger than the area per molecule of perfluorooctanoic acid (2 14nm 2) and muchsmaller than that of ordinary polyacrylic acid (83 4nm 2) . It means that the polymermoleculesin the surface adsorbed layer form the brush structure because of the special effectof the perfluoroalkyl groups at the chain ends .展开更多
文摘Based on the model of random walk on the simple cubic lattice,the distribution function of conformation of a polymer chain in an interfacial layer was deduced.If the model chain was consisted of N segments, it was possible to form both the tail chain, when the terminal segments were adsorbed at the interface, and the adsorbed chain with the non\|terminal group.The conformational number Ω tail of a tail chain is equal to Ω free /(6π N ) 1/2 ,where Ω free is the conformational number of a chain in free state and equals to 6 N for this random walk model. It was found from theoretical analysis that, for the set of a chain attached non\|terminally to the interface, the total conformational number Ω tot is equal to Ω free /6.As an result,the average conformational number m for the chain attached non\|terminally to the interface is Ω \{free\}/6 N .In the case of short chain,for instance N is equal to about 10,the conformational number Ω \{tail\} of tail chain is even larger than the total number Ω \{tot\}. In the limitation of long chain, however, the conformational number Ω \{tail\} for tail chain is nuch large than m,but smaller than Ω \{tot\}. The conclusion is that the distribution function of conformation for chains in the interfacial layer is not uniform,but has a special distribution form described in this paper.
文摘Five samples of perfluoroheptyl end capped polyacrylic acid ( F P A A) having ahigh surface activity were prepared by free radicalpolymerization ofacrylicacid . Theinitiatorwas perfluorooctanoyl peroxide which produced the free radicalof heptyl at 45 ℃. The yieldsof F P A A were in the range of 10 % to 25 % . The weight average molecular weights were2 62 ×104 to 7 99 ×104 and the polydispersity indexes were 1 97 to 5 64 ,depending on theconcentration of the initiator in the monomer. The surface tension was about 15m N/m at30 ℃forthe aqueous solution of F P A Awith the weight average molecular weight2 62 ×104in the concentration of about 0 01g/ m L. The molecular areas of F P A A at the air waterinterface under the condition ofcritical micelle concentration were 3 2 to 4 6n m2 ,which areobviously larger than the area per molecule of perfluorooctanoic acid (2 14nm 2) and muchsmaller than that of ordinary polyacrylic acid (83 4nm 2) . It means that the polymermoleculesin the surface adsorbed layer form the brush structure because of the special effectof the perfluoroalkyl groups at the chain ends .
