226 Introduction to Renewable Biomaterials
O
OO
O
n= 2, divinyl adiapte; n= 8 divinyl sebacat
y= 0, glycerol; y= 1, 1,2,4-butanetriol; y= 3, 1,2,6-hexanetriol
HO
OH
OH
O
OO
O
O
OH
n y
x
Lipase
y –CH 3 CHO
n +
Figure 7.5Lipase-catalyzed polycondensation to prepare linear polyester with free hydroxyl pendant
groups [78].
theα,ω-position of the utilized triol when the polymerization was carried out at 45∘C.
A sugar containing polyester was prepared by lipase-catalyzed polycondensation of
divinyl sebacate and sorbitol in acetonitrile at 60∘C for 72 h [80]. The resulting polymer
hasanaveragemolecularweightof10kDawithexclusiveacylationatα,ω-position
of sorbitol. Carrying out the polymerization reaction at a lower temperature of 20∘C
increased the yield of polymerization process but resulted in polymers with smaller
molecular weight. Potential application of renewable alditol polyols to prepare polyester
with free pendant group was carried out later using N435-catalyzed polycondensation
between adipic acid and various alditol polyols, that is, erythritol, xylitol, ribitol,
d-glucitol, d-mannitol, and d-galactitol [81]. The polymerization process was carried
out in bulk for up to 46 h at temperature of 90∘C. The resulting polyesters had aMw
ranging from 11 kDa (galactitol) to 73 kDa (d-mannitol) without correlation between
sugar reactivity and corresponding chain length.
7.4.3 Polyesters from Fatty Acid-Based Monomers
Vegetable oils are considered as one of the most important renewable platform
chemicals because of their abundant availability in low price [82]. The two main
components that can be derived from vegetable oils are glycerol and fatty acids.
Therefore, utilization of fatty acids to prepare polymers has been shown great interest
over the past two decades [83]. In the field of lipase-catalyzed synthesis of polyesters,
fatty acids were used either as a building block to prepare the polyester main chain or
were introduced to polymer structure as side chains [84].
7.4.3.1 Lipase-Catalyzed Polycondensation of훂,훚-Dicarboxylic Acids and Diols
A series of linear unsaturated or epoxidized thermoplastic polyesters were prepared by
enzymatic polymerization of unsaturated or epoxidizedα,ω-dicarboxylic acid methyl
esters of chain lengths (C 18 ,C 20 ,C 26 ) with 1,3-propanediol or 1,4-butanediol using
N435 as a catalyst [85]. The utilizedα,ω-dicarboxylic acid methyl esters were obtained
from vegetable oils by transesterification reaction of their triglycerides with methanol,
followed by metathetical cleavage of the resulting methyl esters using Grubbs’ catalysts
[86]. The resulting terminally unsaturated fatty acid part was then participated in a
metathetical condensation reaction using Grubbs’ catalysts to yield finally long-chain
symmetrically unsaturatedα,ω-dicarboxylic acid dimethyl esters. The double bond
of the resulting products was then epoxidized using hydrogen peroxides in methyl
acetate and in the presence of N435 as a catalyst. The enzymatic polymerization of
unsaturated or epoxidizedα,ω-dicarboxylic acid methyl esters with 1,3-propanediol
resulted in polyesters with molecular weight in the range of 1950–3300 Da and had
melting points in the range of 47–75∘C, while with 1,4-butanediol polyesters with
