Nanophase separation in side chain polymers: new evidence from structure and dynamics

New evidence for a nanophase separation of incompatible main and side chain parts in amorphous poly( n -alkyl methacrylates) with long alkyl groups are presented. Independent indications for the existence of alkyl nanodomains with a typical dimension in the 1 nm range from studies on dynamics and structure are reported. Results from nuclear magnetic resonance (NMR) experiments are compared with data from different relaxation spectroscopy methods on poly( n -decyl methacrylate). The NMR results in combination with relaxation spectroscopy data support the existence of an independent polyethylene-like glass transition, α PE , within the alkyl nanodomains in addition to the conventional glass transition a at higher temperatures. X-ray scattering data show that the situation in homopolymers is similar to that for random poly( n -alkyl methacrylate) copolymers with the same average length of the alkyl group in the side chains. Scattering data for a series of n -butyl methacrylate samples with polymerization degrees reaching from P =1 to 405 indicate that nanophase separation is chain-length independent above P =25, while the nanophase separation tends to disappear below P =6. Insensitivity of structural aspects in nanophase-separated poly( n -alkyl methacrylates) to changes in the molecular microstructure and consistency of NMR results with independent conclusions from relaxation spectroscopy underline the general importance of nanophase separation effects in a broad class of side chain polymers.