The lattice theory regarding ternary systems involving a conformationally variable polypeptide and a randomly coiled polymer presented recently is extended to the case where an external orientational field is present.Chemical potentials of the components in the isotropic and anisotropic phases were obtained.The calculations carried out show that the external field exerts a marked effect on the phase behavior of the ternary systems.The isotropic-anisotropic biphasic gap is predicted to shift to lower polymer concentrations and become narrower when the external field exists.The entrance of the randomly coiled polymers into the anisotropic phase is promoted.Influences of chain conformation of polypeptide,chain length and temperature have been studied in the presence of the external field.The comparison between theory and experimental results was also carried out.
Phase transitions of polymer liquid crystals may be i nduced not only by changes of temperature or polymer concentration,but also b y external electric,magnetic or other orientational fields.In this paper the pha se behavior of polypeptide liquid crystal solutions,such as PBLG/TCE and PBLG/CH Cl 3/TFA solutions,was studied in the presence of an external electric field.It was found that the liquid crystal phase was stabilized when the external electr ical field was applied and the area of liquid crystal phase was broadened.Qualit atively,the experimental results are in good agreement with the theoretical resu lts calculated by a lattice model previously.The information obtained may be use d to develop new routes for processing rigid flexible block copolymers with be tter mechanical properties and to construct molecular devices for processing and storing information.
Polypeptide graft copolymers such as poly(γ-benzyl-L-glutamate)(PBLG)-poly(ethylene glycol)(PEG) and poly(γ-ethyl-L-glutamate)(PELG)-poly(ethylene glycol)(PEG) were introduced into self-setting calcium phosphate cement(CPC) system to improve its mechanical properties. The compression strength was improved considerably by the induction of polypeptide copolymers. It is about 22.3 higher for PBLG-g-PEG and 65.0 higher for PELG-g-PEG, respectively. The results also show that for the same polypeptide copolymer, higher compression strength of composites can be obtained by introducing copolymer micelles into the CPC. According to the results of scanning electron microscope(SEM), the crystallite shapes of CPC depend on the weight fraction of polypeptide copolymer in the composites.
Self-association behavior of an amphiphilic polypeptide graft copolymer,poly(γ-benzyl L-glutamate)-g-poly(ethylene glycol), and the drug carrier capability of the formed micelles were examined by fluorescence spectroscopy,transmission electron microscopy and UV spectroscopy.It was found that the hydrophobic inner core of the micelles formed by poly(γbenzyl L-glutamate)(PBLG) segments can act as an incorporation site for hydrophobic drugs.The drug-loading content of the graft copolymer micelles tends to be larger when the content of the PBLG segments in the copolymer increases.The results obtained from the drug-release studies showed that the drug-release rates were dependent on the chemical nature of the graft copolymer.
