One of the challenges of developing
bioderived polymers is to obtain
materials with competitive properties. This study investigates the
structure-properties relationships of polyesters and polyethers that
can be derived from d-xylose through metathesis polymerization,
in order to produce bioderived plastic materials that are sourced
from sustainable feedstocks and whose properties can compete with
those of polyolefins such as polyethylene. Bicyclic diol 1,2-O-isopropylidene-α-d-xylofuranose was coupled
with ω-unsaturated fatty acids and alcohols of different chain
lengths (C11, C5, C3), and the resulting
α,ω-unsaturated esters and ethers polymerized via an acyclic
diene metathesis (ADMET) polymerization using a commercial Grubbs
second-generation catalyst, obtaining polymers with M
n up to 63.0 kg mol–1. Glass transition
temperatures (T
g) decreased linearly with
increasing chain length and were lower for polyethers (−32
to 14 °C) compared to polyesters (−14 to 45 °C).
ADMET polymers could be modified postpolymerization by reacting their
internal carbon–carbon double bonds. Thiol–ene reaction
with methyl thioglycolate lowered the T
g while allowing insertion of additional functional groups. Alkene
hydrogenation turned the polyester and polyether with C20 hydrocarbon linkers into semicrystalline polymers with T
m ≈ 50 °C. The latter, when cast into films,
displayed remarkable polyethylene-like properties. Hot-pressed films
proved ductile materials (Young modulus E
y
60–110 MPa, elongation at break εb 670–1000%, ultimate tensile strength σb 8–10 MPa), while uniaxially oriented films proved very strong
yet flexible materials (E
y
190–200 MPa, εb 160–350%, σb 43–66 MPa). Gas barrier properties were comparable
to those of commercial polyolefins. Polyethers were resistant to hydrolysis,
while polyesters depolymerized under alkaline conditions.