Structural and thermal characterization of PTSA doped polypyrrole-polytetrahydrofuran graft copolymer

The thermal degradation processes of p-toluene sulfonate (PTS) doped polypyrrole (PPY) grown from the pyrrole moiety located at both the ends of polytetrahydrofuran (PTHF) have been studied by direct pyrolysis mass spectrometry (DPMS) to gain structural information. To get a better insight, pyrolysis analysis on corresponding homopolymers, PTHF and PPY, have also been carried out. The DPMS data were in accordance with TGA results indicating a significant decrease in thermal stability of the copolymer with respect to both PPY and the matrix polymers. The data also pointed out the degradation of matrix polymer, PTHF during the electrochemical synthesis of polypyrrole on a PTHF coated anode. Although decomposition of matrix polymer occurred, the growth of pyrrole from the pyrrole moieties located at chain ends of PTHF was also confirmed. Thus, it has been proved that a low molecular weight copolymer of polypyrrole involving short chains of PTHF as the end groups has been synthesized

İletken aşı kopolimerlerinin yapısal analizi

TÜBİTAK TBAG Proje01.02.2002Bu çalışmada, iletken polimerlerin mekanik özelliklerini geliştirmek amacı ile elektrokimyasal olarak sentezlenen aşı kopolimerlerinin yapısal analizde direkt piroliz kütle spektrometre ve Curie noktası piroliz kütle spektrometre ve Curie noktası piroliz gaz kromatografi kütle spektrometre teknikleri kullanılmış ve elde edilen kopolimerin blok kopolimer yapısına sahip olduğu saptanmıştır. Sonuçlarımız, direkt piroliz tekniğinin poilimerin yapılarının, ısıl kararlılıklarının ve ısıl bozunun mekanizmalarının belirlenmesinde daha etkin olduğunu göstermiştir. Curie noktası piroliz tekniğinin ise kararlı ısıl bozunum ürünlerinin belirlenmesinde etkili olduğu saptanmıştır

Characterization of polypyrrole/polytetrahydrofuran graft copolymers by direct pyrolysis mass spectrometry

The thermal decomposition pathways and products of pyrrole ended-polytetrahydrofuran (PTHF), p-toluene sulfonate doped polypyrrole (PTS-PPY) and polypyrrole/polytetrahydrofuran (PTS-PPY/PTHF) graft copolymers have been investigated by direct pyrolysis mass spectrometry (DPMS). The data suggest that PTHF degrade via mixed random cleavage and unzipping mechanism followed by hydrogen transfer reactions. Decomposition of dopant in the high temperature range is attributed to a strong interaction between the dopant and the host polymer, whereas the cleavage of the pyrrole ring and lack of high mass fragments are associated with a network structure, Furthermore. evolution of H2O and CO2 lying throughout all pyrolysis temperature range, points out the oxidation of the pyrrole units during electrolysis in aqueous media. Yet, when the trends in the characteristic polypyrrole and dopant based peaks are considered, quite high resemblance to that of pure PTS-PPY is observed. Identical products having identical time-temperature resolved ion current profiles detected at both heating rates, suggest that the thermal deradation characteristics of 9 polypyrrole and dopant are not affected by the presence of the matrix. Significant changes in the matrix-based product peaks from the copolymer spectrum are clearly identified. Such a low pyrolysis temperature, or early appearance of product peaks in the case of ballistic heating, can be directly related to a polymer of very low-molecular weight. The only possible cause for such a trend may be the degradation of the matrix itself during electropolymerization of the pyrrole. Thus, it may be proposed that the stability of PTHF chains totally change during the electrochemical syntheses

Low modulus dry silicone-gel materials by photoinduced thiol-ene chemistry

The curing behavior of telechelic vinyl-functionalized poly(dimethylsiloxane) (PDMS) with poly(dimethylsiloxane-co-propylmercaptomethylsiloxane) using photoinitiated radical thiol-ene polyaddition was studied, by means of rheology, mechanical analysis of the cured elastomeric products, and high resolution magic angle spinning NMR (HR-MAS). Postpolymerization modification of a hydroxy-functionalized PDMS-derivative (OH-PDMS) yielded a telechelic thiol-functionalized PDMS-derivative, which was subsequently used as chain extender for the preparation of dry silicone-gel materials with elastic moduli between 30 and 500 kPa. The rate of thiol-ene polyaddition of the chain extender proved to be similar to that of the cross-linking process using multifunctional PDMS-based thiols. HR-MAS analysis of the loosely cross-linked thiol-ene PDMS networks and their fluoride-solubilized counterparts proved a highly efficient cross-linking with an optimal cure at 1:1 thiol to ene stoichiometric ratios. Using mechanical analysis, it was shown that the low molecular weight thiol-functionalized chain extender was efficiently incorporated in the PDMS polymer network