Polytetrahydrofuran

About: Polytetrahydrofuran is a research topic. Over the lifetime, 735 publications have been published within this topic receiving 6706 citations.

The defect structure of sol–gel-derived silica/polytetrahydrofuran hybrid films by FTIR

Abstract: The structural perturbations induced by polytetrahydrofuran (PTHF) on sol–gel hybrid films were identified by Fourier-transform infrared (FTIR) spectroscopy. The films were prepared by spin-coating, from aged solutions containing tetraethylorthosilicate (TEOS) as the inorganic precursor and different concentrations of PTHF. All the spectra reveal a set of bands that may be associated with structural defects of the silica network. The hybrid films show an additional `defect' band at 560 cm −1 , assigned to a skeletal vibration of 4-fold siloxane rings, whose intensity grows as the polymer content or molecular weight increases. The relative intensity of two components of the νasSi–O–Si mode (resolved by deconvolution of the band at ∼ 1080 cm −1 ) grow accordingly. They were thus assigned to the longitudinal (LO) and transverse optical (TO) modes of that vibration in 4-fold siloxane rings. Simultaneously, the bands assigned to the νSi–O− mode and to the νSi–O(H) mode of unreacted silanol groups (obtained by deconvolution of the band at ∼ 950 cm −1 ) increase. These conjugated observations lead to the conclusion that the polymer hinders the condensation reactions, being responsible for a more porous structure, with retention of a larger proportion of 4-fold siloxane rings. For high concentrations of high molecular weight PTHF, the defect structure of the films indicates that a partial segregation of the polymer occurs.

Infrared thermal analysis of polyurethane block polymers

Abstract: Infrared (IR) thermal analysis was used to study the extent, distribution, and the thermal behavior of hydorgen bonding in MDI-based segmented polyurethane elastomers. Two series of polyurethane elastomers were studied; one was based on a polytetrahydrofuran soft segment (ET series), while the second was based on a poly(tetramethylene adipate) soft segment (ES series). The hard segment in these materials was formed form p, p′-diphenylmethane diisocyanate (MDI) extended with butanediol. Bonded and free NH and C=O infrared absorbances were resolved as a function of temperature using a nonlinear least squares analysis for the fitting of Gaussian curve shapes. Results of this analysis revealed that at room temperature, about 80% of the NH groups in the ET and ES polyurethanes formed hydrogen bonds. In the ET polyurethanes, about 65% of the urethane carbonyls were hydrogen-bonded at room temperature. The extent of interurethane hydrogen bonding was found to be higher in the materials having better pha...

Reversible Mechanochemistry of a PdII Coordination Polymer

Abstract: Breaking up and making up: The ultrasonic cleavage of high-molecular-weight linear coordination polymers of phosphane telechelic polytetrahydrofuran and palladium dichloride in dilute solution is a reversible process (see picture). Sonication for 1 h led to a decrease in the weight-averaged molecular weight of the polymer from 1.7×105 to 1.0×105 g mol−1. Upon leaving the sample to stand for 24 h, the original molecular weight was completely restored.

Polytetrahydrofuran/Clay Nanocomposites by In Situ Polymerization and Click Chemistry Processes

Abstract: Polytetrahydrofuran (PTHF)/clay nanocomposites were prepared by two routes: in situ cationic ring opening polymerization (CROP) and a method involving "click" chemistry. In the first method, PTHF chains were grown from the surface of the organo-modified montmorillonite clay by CROP of tetrahydrofuran (THF) through the hydroxyl functions of the clay by using trifluoromethanesulfonic anhydride, in the presence of 2,6- di-tert-butylpyridine as proton trap and dichloromethane as solvent. The polymerizations were affected by the clay content ratios. The living characteristics of the polymerization were demonstrated by the semilogarithmic first order kinetic plot. In the second method, CROP of THF has been performed independently to produce alkyne- functionalized PTHF and the obtained polymers were subsequently anchored to azide-modified clay layers by a "click" reaction. The exfoliated polymer/clay nanocomposites obtained by both methods were characterized and compared by X-ray diffraction spectroscopy, thermogravimetric analysis, and transmission electron microscopy. Compared to the virgin polymer, the nanocomposites exhibited improved thermal stabilities regardless of the preparation method. However, the nanocomposites prepared by the "click" chemistry approach appeared to be thermally more stable than those prepared by in situ polymerization. Moreover, the "click" chemistry method also provided better exfoliation.