The effect of casting solvent on the material properties of poly(γ‐methyl‐ D ‐glutamate)

Naka

et al. 1978

Polym J

ABSTRACT:A series of poly(r-methyl o-glutamate) (PMDG) films with the different structures were systematically prepared from dichloromethane (DCM)-N, N-dimethylformamide (DMF) solutions. The structures of these films were classified into three types, vix., phase I, phase M, and phase C as obtained in a previous work from DMF, 1, 2-dichloroethane and DCM, respectively. Observation of the PMDG films cast from ch!oroform-DMF solutions, showed that phase C arises from the phase which consists of the cholesteric liquid crystal structure, and it was assumed that the crystallites in phase C should be divided into mosaic blocks. Three mechanical dispersions were observed at 160, 190°C, and above 200°C. The a1 dispersion (at 160°C) was associated with the molecular relaxation in phase I, and further, the a 3 dispersion (above 200°C) was related to the molecular motion of a-helices in phase M with the cholesteric twisted structure. For the a2 dispersion (at 190°C) commonly observed for phase C, two relaxation mechanisms are discussed: the molecular motion of ahelices in phase C and the mutual displacement of the neighboring crystallites. The PMDG films cast from m-cresol at various temperatures and the PMDG-poly(r-methyl L-glutamate) (PMLG) blend films cast from chloroform solutions, showed a remarkable shift of a 2 loss peak temperature. To explain this shift in peak temperature, the latter mechanism seems reasonable for the a 2 dispersion.KEY WORDS Poly(r-methyl glutamate)/ Casting History/ Cast Film/ Mechanical Dispersion / X-Ray Diffraction / Depending on the solvent and polypeptide concentration, a polypeptide molecule may exist in a number of conformations in solution. 1 Solvents are categorized into random coil and helical types. The random coil solvents are generally very polar and form strong hydrogen bonds with the polypeptide molecules. Dichloroacetic acid (DCA) and trifluoroacetic acid (TFA) are random coil solvents for many polypeptides in dilute solution. Most chlorinated hydrocarbons such as chloroform and DCM, with DMF and m-cresol, favor formation of the helical form of the polypeptide. chain structure has been observed in the films swollen in formic acid and in crystals precipitated from dilute solution containing formic acid. 2 This structure is also obtained from TFA or DCA solution, depending on the casting velocity. 3 Thus, when the films are cast from random coil solvents, the chain conformation in the films is not only in the helical form, but also partially in the /3-chain form.Poly(r-methyl glutamate) is known to be soluble also in the coil form in such solvents as DCA and TF A, and in the helical form in helicogenic solvents such as m-cresol and chloroform. However, when films are prepared from random coil solvents, the chain conformation in the films is mainly in the helical form. On the other hand, the /3-No conformational change is observed when the films are cast from the helicogenic solvents. Thus, in this solvent system, the association or aggregation of a-helices 4 -6 is of interest. In a...

Section: Mechanical Properties Of Pmdg Films and Pmdg -Pmlg Blendmentioning

confidence: 72%

Structure and Mechanical Properties of Poly(γ-methyl glutamate) Films. II.

Naka

et al. 1978

Polym J

J. Polym. Sci. B Polym. Phys.

“…Since their conformation can be easily changed by varying the temperature of the solvent in the solution, synthetic poly(peptide) is expected to be a material with a molecularly ordered membrane having several functions. 1 In particular, the ␣-helical structure of a poly(peptide) with photosensitive side chains was studied because it makes the energy transfer 2 of the charge transfer along the polymer chain easier.…”

Section: Introductionmentioning

confidence: 99%

Charge transport properties for carbazolyl groups pendant poly(glutamate)

Yoshida

Mitsui

Kawai

et al. 1999

Carbazolyl groups pendant poly(glutamate) (PCLG) was prepared to analyze its charge‐transport properties by employing mobility measurements and thermally‐stimulated current (TSC) measurements. The mobility induced TSC (MITSC) model proposed by I.Chen was employed to evaluate the experimental TSC spectra with mobility results. Simulated MITSC spectra showed good agreement in its peak temperature with experimental TSC spectra for PCLG. This suggests that the carrier transport followed the trap‐limited mechanism estimated by the mobility results. Further, the peaks in experimental TSC spectra appeared over the same temperature range as that in thermally‐stimulated polarization current (TSPC) spectra. Since the TSPC spectra were found to be correlated with the dielectric tan δ spectra for PCLG, the peaks in TSPC spectra are attributed to the side‐chain relaxation for PCLG. Therefore, the similarity between TSPC and TSC spectra indicates that the charge‐transport mechanism for PCLG was considerably affected by side‐chain relaxation for PCLG, which would vary the energy state of trap sites and effectively reduces the energy for the release of the carriers trapped on the illuminated surface. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 61–69, 1999

J. Polym. Sci. B Polym. Phys.

“…In our studies, we pay attention to the ordered structure of polypeptide and utilize its structure for preparing high‐charge transport materials. Since their conformations can be changed by varying temperature or solvent, synthetic polypeptides are regarded as promising materials for molecularly ordered membranes having various functions 4. Particularly, the α‐helical structure of polypeptides with photosensitive side chains was studied for energy transfer5 and for charge transfer along the polymer chain.…”

Section: Introductionmentioning

confidence: 99%

Charge transport properties of triphenylamine-pendant polypeptide

Yoshida

Ayano

Kobayashi

2000

The structurally ordered polymer, triphenylamine‐pendant polypeptide (PATPA: poly[γ‐4‐(N,N‐diphenylamino‐phenyl)‐L‐glutamine]), was prepared in order to obtain high hole mobility and high thermal stability. The hole mobility obtained for PATPA (ca. 10−5 cm2/Vsec) at room temperature is higher than that for poly(N‐vinylcarbazole) (PVK) (ca. 10−7 cm2/Vsec) or that of carbazole‐pendant polypeptide (PCLG) (ca. 10−8 cm2/Vsec). These results are supported by thermally stimulated current (TSC) measurements because the TSC can be correlated with the mobility. The glass‐transition temperature (Tg) of PATPA was estimated to be about 130° by differential scanning calorimetry (DSC). From these results, PATPA is an alternative candidate as a photoconductive polymer with high thermal stability and high hole mobility. The ordered structure along the main chain is thought to facilitate hole transport. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 362–368, 2000