Dispersion-dependent free volume behavior in polycarbonate/strontium titanate nanocomposites
Journal of Polymer Research, cilt.33, sa.8, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 33 Sayı: 8
- Basım Tarihi: 2026
- Doi Numarası: 10.1007/s10965-026-05064-5
- Dergi Adı: Journal of Polymer Research
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Chemical Abstracts Core, Compendex, INSPEC, Academic Search Ultimate (EBSCO), Engineering Source (EBSCO), Materials Science & Engineering Collection (ProQuest), Technology Collection (ProQuest)
- Anahtar Kelimeler: Free volume, Polycarbonate/SrTiO₃, Positron annihilation, Variable energy positron beam
- Marmara Üniversitesi Adresli: Evet
Özet
Polycarbonate-based nanocomposites incorporating varying concentrations (0–7 wt%) of strontium titanate (STO) were fabricated via spin-coating. X-ray diffraction (XRD) analysis indicated that the crystallinity of the polycarbonate matrix remained largely unaffected at STO loadings up to 5 wt%; however, a significant increase in crystallinity was observed at 7 wt%. Atomic force microscopy (AFM) revealed that higher STO content correlated with improved surface homogeneity. Free volume characteristics were investigated using positron annihilation lifetime spectroscopy (PALS), coincidence Doppler broadening spectroscopy (CDBS), and variable energy positron beam (VEPB) techniques. The results demonstrated that, with the exception of the 5 wt% STO composition, the incorporation of STO nanoparticles reduced free volume by restricting polymer chain mobility. The anomalous behavior at 5 wt% is attributed to poor nanoparticle dispersion, which promoted void formation. Depth-profiling analysis conducted via VEPB further revealed that surface regions exhibit higher free volume compared to the bulk. The observed non-monotonic behavior is tentatively attributed to a competition between polymer–filler interfacial interactions (plausibly involving polar interactions with the filler surface) and filler aggregation, though the chemical nature of these interactions remains speculative without direct spectroscopic evidence.