Perspective
Crosslinked Polymers Based on Monomers Derived from Renewable Resources
and Their Application Potential
Veronika Strehmel* and Bernd Strehmel
Niederrhein University of Applied Sciences, Faculty of Chemistry and
Institute for Coatings and Surface Chemistry, Adlerstrasse 32, D-47798
Krefeld, Germany
E-mail:
veronika.strehmel@hsnr.de
Abstract
Possible structural variation of a bio-based dimethacrylate derived from
oleic acid and ethylene glycol is discussed as well as sources to obtain
the starting material for manufacturing of this monomer. Furthermore,
aspects influencing the transfer of a newly developed product or further
scientific result to application are included into the discussion as
well focusing to manufacturing processes and development of a new
product for the market.
KEYWORDS
bio-based monomer, dimethacrylate, photo-initiated polymerization,
crosslinked polymer, application potential
INTRODUCTION
Nowadays, there is no doubt that the modern society demands to search
for alternative materials having the capability to replace fossil
resources partially or completely in the future. Generation of fossil
resources has needed a long period in the earth’s history. Nevertheless,
they have been used with continuous increasing amount in the last two
centuries to generate materials. Thus, this topic closely relates to the
chemical industry that has used fossil resources as both starting
material for product manufacturing and energy source, which appears as
very important for the usually highly energy intensive chemical
processes. Two ways appear purposeful to solve this problem. These ways
include both renewable energy sources and renewable materials. Sunlight
seems useful as direct or indirect renewable energy source. Various
plants produce a broad variability of biomass catalyzed by enzymes in
the presence of sunlight as well. Discussions have continued in the
literature to search regarding selection of available plant species
outside the competition with food production for humans and animals,
efficiency of product manufacturing from biomass, and re-using the
material after its application.[1-4] Beside the
high molecular weight natural products, such as cellulose, hemicellulose
and lignin, low molecular weight compounds have received increased
interest recently.[4-6] The latter include
terpenes and triglycerides, as well as products derived from
triglycerides like glycerin and various fatty acids. Nevertheless, some
of them interfere the food chain, which appears critical in countries
with high population density or regions with food shortage. Thus,
resources based on waste have moved into the focus.
Furthermore, several bio-based linear aliphatic, aromatic, and
cycloaliphatic compounds have been successfully converted into
(meth)acrylates that are interesting monomers for manufacturing of
polymers.[7-14] Among these bio-based monomers is
a new dimethacrylate synthesized in three steps as shown in Scheme 1.
The synthesis starts with esterification of oleic acid with ethylene
glycol, it continues with epoxidation of the two double bonds of the
ethylene dioleate, and ring opening reaction of the resulting diepoxy
compound with methacrylic acid is the final
step.[12] Moreover, the new bio-based
dimethacrylate was polymerized in thin film using photoinitiated radical
polymerization mechanism applying ultraviolet-technology (Scheme 1) to
form an insoluble crosslinked polymer film showing high hydrophobicity
detected by contact angle measurements.[12]Crosslinking polymerization of the bio-based dimethacrylate alone or in
the presence of further bio-based methacrylates comprising aromatic
structures resulted in glass transition temperature increase of the
highly hydrophobic crosslinked polymer films that makes them interesting
for application e. g. as water-repellent coating for surface protection.
The latter may be of importance for surface protection against
corrosion. Such materials possess additionally potential in medical
application as long as the natural origin would not cause incompatible
responses of the body that synthetic materials sometimes do.