The influence of alkyl substituents of POSS in polyethylene nanocomposites

The influence of the alkyl substituent of POSS containing Q8 cage in polyethylene (PE) – POSS nanohybrids was investigated in this paper. Octakis(dimethylsiloxy)octasilsesquioxanes bearing linear and branched alkyl substituents, chain length varying between C3 and C8 for the straight-chain derivatives and between C5 and C7 for the branched-ones have been prepared for this purpose. XRD analysis showed that POSS coalesced in amorphous aggregates even if the pristine POSS was crystalline and the amount of these aggregates decreases with the increased length of the alkyl substituent. Peak force QNM mode of AFM revealed the presence of high modulus poor-POSS-domains and low modulus rich-POSS-domains whose size was around 140 nm for the octapropyl substituted POSS composite and vary in the range 50–90 nm for the composites with longer alkyl substituents on POSS. Although improved compatibility and dispersion was highlighted for POSS with long alkyl substituents, short length linear alkyl substituents (e.g. propyl) for POSS are preferred for improvements in tensile strength and thermal stability.