Polytetrahydrofuran applications

This equation is applicable to such a system as liquid tetrahydrofuran-dissolved polytetrahydrofuran which was discussed in part 3 of this review. 

The application of refractive index and differential viscometer detection in SEC has been discussed by a number of authors [66-68]. Lew et al. presented the quantitative analysis of polyolefins by high-temperature SEC and dual refractive index-viscosity detection [69]. They applied a systematic approach for multidetector operation, assessed the effect of branching on the SEC calibration curve, and used a signal averaging procedure to better define intrinsic viscosity as a function of retention volume. The combination of SEC with refractive index, UV, and viscosity detectors was used to determine molar mass and functionality of polytetrahydrofuran simultaneously [70]. Long chain branching in EPDM copolymers by SEC-viscometry was analyzed by Chiantore et al. [71]. 

Unfortunately, films formed by 25 d are still quite tacky which make them unsuitable for these applications. Visualization of air flow over objects such as aircraft requires materials which provide a smooth, abrasive resistant surface. With this in mind, the cationic chain end of 19 (see Scheme 1) was reacted with tetrahydrofuran resulting in polythionylphosphazene-h-polytetrahydrofuran block copolymer (30 and 31) [46] ... 

The oligo-polyol s viscosity is determined using a Brookfield viscosimeter. The Standard Test Method for oligo-polyol viscosity determination is ASTM D4878 [37]. There are two test methods, A and B, applicable for viscosities between 0.01 to 1000 Pa-s, at 25 °C, or for solid polyols (such as polytetrahydrofuran), at 50 °C. Test method A is indicated for oligo-polyols of very high viscosities. 

Recently in the Sijbesma group, high-molecular-weight linear coordination polymers of diphenylphosphine telechelic polytetrahydrofuran with palladium (II) dichloride were developed [3]. Molecular weights of these polymers could be altered reversibly by ultrasotmd and it has been shown that polytetrahydrofuran chains remain intact during sonication [78]. This implies that only the reversible palladium-phosphorus bonds are broken and coordinatively unsaturated palladium complexes were produced by the application of mechanical forces on these coordination polymers [79]. Furthermore, polymers which include both Pd and Pt were sonicated and it was shown that force selectively breaks the weaker Pd-phosphine bonds which were randomly distributed along the polymer backbone [80]. 

Poly (thiophene)s are of particular interest as electfochromic materials owing to their chemical stability, ease of synthesis and processability. For the most part, current research has been focused on composites, blends and copolymer formations of several conjugated polyheterocyclics, polythiophene and its derivatives, especially PEIX)T. In one example, poly(3,4-ethylenedioxythiophene) (PEDOT)/poly(2-acrylamido-2-methyl-l-propanesulfonate) (PAMPS) composite films were prepared by Sonmez et al. for alternative electrochromic applications [50]. Thin composite films comprised of PEDOT/PAMPS were reported to switch rapidly between oxidized and neufial states, in less than 0.4 s, with an initial optical contrast of 76% at A.max. 615 nm. Nanostructured blends of electrochromic polymers such as polypyrrole and poly(3,4-ethylenedioxythiophene) were developed via self-assembly by Inganas etal. for application as an electrochromic window [26]. Uniir etal. developed a graft-type electrochromic copolymer of polythiophene and polytetrahydrofuran for use in elecfiochromic devices [51]. Two EDOT-based copolymers, poly[(3,4-ethylenedioxythiophene)-aZ/-(2,5-dioctyloxyphenylene)] and poly[(3,4-ethylenedioxythiophene)-aft-(9,9 -dioctylfluorene)] were developed by Aubert et al. as other candidates for electrochromic device development [52],... 

The addition of antihydrolysis agents is required in many engineering applications. Particularly useful are diarylcarbodiimides with alkyl substituents in an ortho-position to the -N=C=N group. Although polyethers, such as polytetrahydrofuran, are not hydrolytically degraded because of their chemical structure, in Europe considerably more polyester is used than polyether. This can be explained by the positive effect of carbodiimides as hydrolysis stabilizers that are tailored to specific applications. The additive load ranges from 0.5 to 2%. Its protective effect is not influenced by whether carbodiimide is added directly to the polyester or to the prepolymers. In... 

---