Dynamic shear oscillation measurements at small strain were used to characterize the viscoelastic properties and related differences in the molecular structure of hydrogels based on gelatin methacrylamide. Gelatin was derivatized with methacrylamide side groups and was subsequently cross-linked by radical polymerization via photoinitiation. The light treatment of methacrylamide gelatin solutions resulted in the production of hydrogel films with high storage modulus (G'). Mechanical spectra and thermal scanning rheology of the obtained hydrogels are described. The temperature scan of the network below and above melting point of gelatin allowed us to identify the respective contributions of chemical and physical cross-linkage to the hydrogel elastic modulus. The results indicate that the rheological properties of the gelatin-based hydrogels can be controlled by the degree of substitution, polymer concentration, initiator concentration, and UV irradiation conditions.

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Cloud-point curves by DSC measurements at different scanning rates on solutions of two samples of poly(vinyl methyl ether) in water show two minima in a temperature−composition plot. The significance of the data was confirmed by static measurements of the coexisting-phase compositions and phase-volume ratios. A thermodynamic analysis in terms of a strongly concentration-dependent interaction parameter leads to the conclusion that the system H2O/PVME exhibits so-called type III behavior. For polymers of infinite molar mass, such behavior is characterized by the occurrence of two off-zero critical concentrations, in addition to the usual zero critical concentration marking the ϑ state.

The isothermal crystallization of three different types of poly[ε-caprolactone-co-ethylene glycol] (PCL−PEG) incompatible block copolymers [A−B, (A)2−B, and A−B−A] was investigated using DSC. The PEG weight fraction in the copolymers was slightly varied from 18 to 22 wt %. It was established that the kinetic parameters from the Avrami equation (the half time of crystallization, τ0.5, and the rate constant of overall crystallization, z) for the PCL constituent, which crystallizes first, are similar to the kinetic parameters of the corresponding homopolymer (PCL). The growth retardation of the constituent which crystallizes second (PEG block) is attributed to the mutual influence between the PEG constituent and the PCL crystal phase which fixes (hardened) the total copolymer structure.

Structural investigation in systems of anionic polyelectrolytes and dodecyl-(DPC) and cetylpyridinium chlorides (CPC) were performed at various surfactant to polyelectrolyte (S/P) ratios using synchrotron X-ray scattering. The polyelectrolytes used were sodium poly(styrenesulfonate) (NaPSS), poly(acrylate) (NaPA), and poly(methacrylate) (NaPMA). From the Bragg peaks emerging in the scattering curves, different types of organization of the surfactant in conjunction with the polyion are proposed. They depend on the surfactant chain length, on the polyelectrolyte chemistry, and on the S/P value: (1) NaPSS/DPC (all S/P values), NaPSS/CPC (S/P < 1), and NaPA(NaPMA)/DPC (S/P < 1) complexes produced a micellelike organization of the surfactant along the polyion chain. The NaPSS-induced micelle is smaller in size than the ordinary one because of the inclusion of the aromatic rings on the PSS chain into the hydrophobic interior of the micelle. The size of the ordered elements in complexes with the hydrophilic NaPA and NaPMA corresponds to the radius of an ordinary globular micelle together with the thickness of the polyelectrolyte chain that surrounds it. (2) In NaPSS/CPC precipitate (S/P g 1), a hexagonal phase is observed with a unit cell parameter equal to 39.5 Å. (3) The multiple reflections in the scattering curves of NaPA(NaPMA)/DPC complexes with S/P g 1 and of NaPA(NaPMA)/CPC ones for all S/P values point to some cubic structure. The cell constants of these mesophases correspond approximately to 2.5 diameters of a globular surfactant micelle. (4) In addition to a cubic phase, a well-pronounced hexagonal phase with a unit cell parameter of 40.5 Å develops in the NaPA/CPC case with S/P g 1.

Pure cellulose p-toluenesulfonates (tosylates) with an insignificant formation of chlorodeoxy groups were prepared by reacting cellulose dissolved in a solution of N,N-dimethylacetamide and LiCl with tosylchloride (Tos-C1) in the presence of triethylamine within 24 h at 8 "C. Various cellulosic starting materials with a degree of polymerization from 280 to 5 100 were used. The samples obtained were characterized by means of elemental analysis, FTIR and I3C NMR spectroscopy, and their intrinsic viscosities. The rise of the molar ratio of Tos-CVanhydroglucose unit (AGU) from 0.6 to 9.0 leads to an increase in the degree of substitution (DS) from 0.4 up to a maximum value of 2.3. The cellulose tosylates are readily soluble in common organic solvents like dimethyl sulfoxide (within the whole DS range) and in N,N-dimethylacetamide, N,N-dimethylformamide, acetone, tetrahydrofuran and trichloromethane depending on DS. As revealed by 13C NMR spectroscopy a faster tosylation takes place at the 0-6 atom of AGU compared with the 0-2/3 atoms. This was additionally confirmed by analysis of the corresponding iododeoxy celluloses synthesized with NaI in acetylacetone. Furthermore, some important properties as stability against alkaline and heat were studied as well. ZUSAMMENFASSUNG:Cellulose-p-toluolsulfonsaureester (Cellulosetosylate) lassen sich durch homogene Umsetzung von Cellulose in einer Losung aus N,N-Dimethylacetamid und LiCl mit Tosylchlorid (Tos-C1) und Triethylamin in 24 h bei 8 "C in hoher Ausbeute und mit minimalem Einbau von Chlordesoxy-Gruppen herstellen. Die unterschiedlichen Celluloseausgangsmaterialien hatten durchschnittliche Polymerisationsgrade von 280 bis 5100. Die Produkte wurden mit Elementaranalyse, 13C-NMR-und FTIR-Spektroskopie und durch Bestimmung der Grenzviskositaten charakterisiert.Die Erhohung des Molverhaltnisses Tos-Cl/Anhydroglucose-Einheit (AGU) von 0.6 auf 9.0 fiihrte zu einem Anstieg des Substitutionsgrades (DS) von 0.4 bis auf einen Maximalwert von 2.3. Die Cellulosetosylate sind in herkommlichen organischen Losungsmitteln wie Dimethylsulfoxid (im gesamten DS Bereich) und in N,N-Dimethylacetamid, N,N-Dimethylformamid, Aceton, Tetrahydrofuran und Trichlormethan (in Abhangigkeit vom DS) loslich. Durch '3C-NMR-Spektroskopie wurde nachgewiesen, dal3 die Tosylierung am 0-6 Atom der AGU schneller als an den 0-2/3 Atomen erfolgt. Die Analyse der korrespondierenden Ioddesoxycellulosen, die durch Umsetzung mit NaI in Acetylaceton synthetisiert wurden, bestatigte dies zusatzlich. Dariiber hinaus wurden wichtige Eigenschaften der Cellulosetosylate wie die Stabilitat gegeniiber Alkali und thermischer Beanspruchung untersucht.

Equilibrium swelling of networks capable of separating into a highly swollen and a collapsed phase is discussed on the basis of a concentration-dependent pair interaction parameter. Classic rules, to be obeyed by the various binodals and their metastable and unstable extensions, rationalize the experimentally accessible portions of the phase diagram and are covered by a simple model yielding acceptable parameter values when fitted to swelling data on the system water/polyW-isopropylacrylamide). The description of the solvent/network binodal is good, but the predicted location of the LCST miscibility gap for linear chains deviates considerably from the measured cloud points. It is probable that linear and branched chains do not differ much in enthalpic contributions to the interaction parameter but deviate appreciably in the entropic terms. This feature offers an acceptable explanation for the discrepancy.