Structural Studies of Nanophase-Separated Poly(2-hydroxyethyl methacrylate)-l-polyisobutylene Amphiphilic Conetworks by Solid-State NMR and Small-Angle X-ray Scattering

• Published in: Macromolecules 2003-12, Vol.36 (24), p.9107-9114
• Main Authors: Domján, Attila, Erdödi, Gábor, Wilhelm, Manfred, Neidhöfer, Michael, Landfester, Katharina, Iván, Béla, Spiess, Hans Wolfgang
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Properties and characterization; Structure, morphology and analysis
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma034891h

Bicomponent nanophase-separated poly(2-hydroxyethyl methacrylate)-linked-polyisobutylene (PHEMA-l-PIB) amphiphilic conetworks were synthesized by radical copolymerization of methacrylate−telechelic polyisobutylene (MA−PIB−MA) and different amounts of 2-(trimethylsilyloxy)ethyl methacrylate (SEMA) followed by quantitative hydrolysis of the trimethylsilyl protecting groups. The PIB content of the resulting conetworks, determined by elemental analysis and solid-state 1H NMR under fast magic-angle spinning (MAS), varied between 17 and 63% w/w. Phase separation and morphology of these conetworks were investigated by DSC, small-angle X-ray scattering (SAXS), and for the first time by 1H spin diffusion solid-state NMR. Two T g values were observed by DSC in all samples. The observed T g values were close to the literature values of both homopolymers (110 °C for PHEMA and −67 °C for PIB), indicating a strong phase-separated morphology in these conetworks. Parameters were optimized for the 1H spin diffusion NMR experiments, and the measurements were carried out with six filtering cycles and a 10 μs delay between pulses at 90 °C. The NMR and SAXS measurements prove strong phase-separated morphology. The sizes of the hydrophilic (PHEMA) and hydrophobic (PIB) nanodomains were determined to be in the 5−15 nm range. The spin diffusion experiments also indicate strongly separated phases without a detectable interface with mixed components. The long period of our system seems to depend weakly on the volume fraction whereas the morphology of the nanophases depends on the volume fraction.