(214d) Modifying the Surface Properties of Wood Using ATRP Grafting Polymerization

Wood is a well-known bio-based material which
can be used for a wide range of applications, with a major focus on its
utilization as a building material. In order to profit from its natural
properties and to develop smart and innovative materials, a variety of chemical
modifications can be used. Cabane et al. have shown
that wood can be modified by in-situ grafting of
synthetic polymers enhancing the natural properties of wood and making it
competitive with other available materials [1]. We recently extended the
modification of wood through the grafting of fluorinated acrylates by
surface-initiated ATRP (Fig 1A). ATRP is a living polymerization technique
allowing for a better control over grafted polymer chain length. The polymer
chains are grafted from the wood biopolymers through a
two-step reaction. In the first step the ATRP initiator is grafted onto the
wood surface (via esterification), and it is used in the second step to grow
the polymer chains.

Several techniques were used to
characterize the wood properties after the polymerization. Amongst others, the
most outstanding results obtained were in regard to
the wettability. Through the functionalization of wood with a fluorinated
polymer, and following the examples of superhydrophobic
surfaces found in nature, we have acquired a renewable material that is both superhydrophobic and oleophilic. The
contact angles of water on the wood surface measured before and after
modification increase drastically with values raising from 73º to 180 º (Fig
1B). This increase is both due to the chemical modification and the surface
roughness acquired by the combination of the both the natural roughness of wood
and the grafted polymer chains.

Moreover, quaternary amine acrylates were
grafted onto the wood in order to further study the wettability given by
the combination of the natural structure of wood and the chemical and physical
properties of the polymer introduced. Both quaternary amines and fluorinated
acrylates have been separately and successfully grafted
into wood (Fig. 1C) offering different wettabilities
(Fig 1D). In further work we would like to extend the
methods used to copolymerize fluorinated and quaternary amine acrylates,
combining the properties of both polymers. By this copolymerization
it would be possible to obtain a material that is both hydrophilic and oleophobic [2]. This new material could
be used to extract the oil present in contaminated water resources.

Fig. 1: A) Wood modification scheme; B) Contact
angle measurements of water on the wood surface; C) FTIR spectra; D) Wettability
of wood with various liquids.

[1].  E.
Cabane, T. Keplinger, V. Merk, P. Hass, I. Burgert, ChemSusChem 2014, 7, 1020-1025.

[2]. P. Brown,
O. Atkinson, J. Badyal, ACS Applied Materials & Interfaces 2014, 6, 7504-7511.