Polymer Chemistry Blog

The ability to modify surfaces with polymers has been readily exploited to alter various surface properties, such as wettability, biocompatibility and chemical functionality. Covalently-bound polymer-grafted surfaces can be prepared either through a “grafting-from” or “grafting-to” approach.

“Grafting-from” entails the modification of the surface, followed by polymerisation of monomer units from the modified surface. “Grafting-to” is achieved when a pre-formed polymer chain is coupled to a functional surface. Various surfaces have been investigated for polymer grafting, both planar surfaces and 3D morphologies such as nanoparticles.

This month we take a look at three articles, published in Polymer Chemistry, which report polymer-grafted surfaces, via surface-initiated “grafting-from”  polymerisations in all cases, and in one article the authors have compared the “grafting-from” approach to “grafting-to”. In each report the properties of the respective substrates have been dramatically altered by the polymer grafting.

SiO₂ nanoparticles were utilized for the grafting of PHEMA and PBzMA by RAFT polymerisation. The PHEMA/PBzMA grafted SiO₂ nanoparticles were prepared through first, growing PHEMA chains from the surface, subsequent immobilisation of more RAFT agent onto the SiO₂ surface, then polymerisation of BzMA. The grafted nanoparticles were observed to self-assemble, which was proposed to be due to phase separation of the two blocks and hydrophobic interactions between PBzMA domains.

A dopa-functional photoiniferter was used to polymerise NiPAAm, DMAEMA and NVP by UV photopolymerisation. These pre-formed polymers were subsequently grafted-to a titanium surface through the dopa groups. Comparatively, a gold surface was functionalised with the dopa photoiniferter followed by polymerisation from the surface (grafting-from). In each case grafting was confirmed by XPS and contact angle measurements, showing efficient functionalisation of the substrates.

Polyacetylene based ladder-like polymer brushes were grafted-from gold surfaces and investigated for their long-term stability and conductivity. The doped conjugated polyacetylene was less susceptible to degradation/oxidation when supported by another chain. The stability was improved when the surface grafting density was higher and the conductivity was only reduced by 1 order of magnitude after storage in air at room temperature for 6 months.