Albert J. J. Woortman

Enzymatic Synthesis of Biobased Polyesters Using 2,5-Bis(hydroxymethyl)furan as the Building Block

2,5-Bis(hydroxymethyl)furan is a highly valuable biobased rigid diol resembling aromatic monomers in polyester synthesis. In this work, it was enzymatically polymerized with various diacid ethyl esters by Candida antarctica Lipase B (CALB) via a three-stage method. A series of novel biobased furan polyesters with number-average molecular weights (M(n)) around 2000 g/mol were successfully obtained. The chemical structures and physical properties of 2,5-bis(hydroxymethyl)furan-based polyesters were fully characterized. Furthermore, we discussed the effects of the number of the methylene units in the dicarboxylic segments on the physical properties of the furan polyesters.

A biocatalytic approach towards sustainable furanic–aliphatic polyesters

An eco-friendly approach towards furanic–aliphatic polyesters as sustainable alternatives to aromatic–aliphatic polyesters is presented. In this approach, biobased dimethyl 2,5-furandicarboxylate (DMFDCA) is polymerized with various (potentially) renewable aliphatic diols via Candida antarctica Lipase B (CALB)-catalyzed polymerization using a two-stage method in diphenyl ether. A series of furanic–aliphatic polyesters and oligoesters is successfully produced via enzymatic polymerization. Some products reach very high (weight average molecular weight) values of around 100 000 g mol−1. Studies on the effect of the diol structure on the enzymatic polymerization indicate that CALB prefers long-chain alkane-α,ω-aliphatic linear diols containing more than 3 carbons. We also found that the molecular weights of the obtained furanic–aliphatic polyesters increase steadily with the increase of reaction temperature from 80 to 140 °C. MALDI-ToF MS analysis reveals that five polyester species may be present in the final products. They were terminated with the ester/–OH, ester/ester, –OH/–OH, no end groups (cyclic), and ester/aldehyde groups, respectively. Furthermore, the structure–property relationships were studied by comparing the crystalline/thermal properties of a series of relevant furanic–aliphatic polyesters.

Influence of lysophosphatidylcholine on the gelation of diluted wheat starch suspensions

Starch is an omnipresent constituent which is used for its nutritional and structuring properties. Recently concerns have been raised since starch is a source of readily available glucose which is tightly correlated with diabetes type II and obesity. For this reason, the possibilities for modulating the digestibility of starch while preserving its functional properties were investigated; therefore the focus of this paper is on starch gelatinization and the effect of lysophosphatidylcholine (LPC) on the structuring properties of wheat starch. The effect of LPC on thermal properties and viscosity behavior of starch suspensions was studied using DSC and RVA, respectively. The influence on granular structure was observed by light microscopy. The RVA profile demonstrated no viscosity increase at high LPC concentrations which proves intact granular structure after gelatinization. LPC in intermediate concentrations resulted in a notable delay of pasting; however the peak and end viscosities were influenced as well. Lower LPC concentrations demonstrated a higher peak viscosity as compared with pure starch suspensions. DSC results imply that inclusion complexes of amylose-LPC might be formed during pasting time. Since the viscosity profiles are changed by LPC addition, swelling power and solubility of starch granules are influenced as well. LPC hinders swelling power and solubility of starch granules which are stimulated by heating.

Facile preparation method for inclusion complexes between amylose and polytetrahydrofurans.

Several methods were used to investigate the possibility of preparing inclusion complexes between amylose and polytetrahydrofurans (PTHF) via direct mixing. Potato amylose (M(v) ∼ 200 kg/mol) and synthetic amylose (M(n) 42 kg/mol) were complexed with PTHF having different molecular weights (M(n) between 650 and 2900 g/mol) to study the effect of the length of the host and the guest molecules on the complexation. The resulted products were studied by differential scanning calorimetry (DSC) that showed a characteristic melting peak in the range of 120-140 °C. Emulsification of both amylose and polytetrahydrofuran improved the complexation. The largest amount of complexes was obtained with shorter PTHF chains, which also resulted in less amylose retrogradation. Furthermore, PTHF chains with similar molecular weight but different end groups were used. Amine terminated PTHF formed a higher amount of complexes compared to the hydroxyl terminated PTHF. However, no amylose complexes were formed using benzoyl terminated PTHF with low molecular weight. This is due to the bulky group of benzoyl, which indicates that the mechanism of the complexation between amylose and PTHF occurs via insertion rather than wrapping. In addition, X-ray diffraction (XRD) analysis showed that the included PTHFs induced the formation of the so-called V-amylose with six glucose residues per helix turn. Some additional diffraction peaks indicate that the induced V(6)-amylose is probably an intermediate or the mixtures between V(6I)- and V(6II)-amylose.

Enzyme-Catalyzed Synthesis of Unsaturated Aliphatic Polyesters Based on Green Monomers from Renewable Resources

Bio-based commercially available succinate, itaconate and 1,4-butanediol are enzymatically co-polymerized in solution via a two-stage method, using Candida antarctica Lipase B (CALB, in immobilized form as Novozyme® 435) as the biocatalyst. The chemical structures of the obtained products, poly(butylene succinate) (PBS) and poly(butylene succinate-co-itaconate) (PBSI), are confirmed by 1H- and 13C-NMR. The effects of the reaction conditions on the CALB-catalyzed synthesis of PBSI are fully investigated, and the optimal polymerization conditions are obtained. With the established method, PBSI with tunable compositions and satisfying reaction yields is produced. The 1H-NMR results confirm that carbon-carbon double bonds are well preserved in PBSI. The differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) results indicate that the amount of itaconate in the co-polyesters has no obvious effects on the glass-transition temperature and the thermal stability of PBS and PBSI, but has significant effects on the melting temperature.

Size exclusion chromatography with multi detection in combination with matrix-assisted laser desorption ionization-time-of-flight mass spectrometry as a tool for unraveling the mechanism of the enzymatic polymerization of polysaccharides.

Determination of the size distributions of natural polysaccharides is a challenging task. More advantageous for characterization are well-defined synthetic (hyper)-branched polymers. In this study we concentrated on synthetic amylopectin analogues in order to obtain and compare all available data for different distributions and size dependence of molecular weights. Two groups of well-defined synthetic branched polysaccharides were synthesized via an in vitro enzyme-catalyzed reaction using the enzyme phosphorylase b from rabbit muscle and Deinococcus geothermalis glycogen branching enzyme. Synthetic polymers had a tunable degree of branching (2%-13% determined via (1)H NMR) and a tunable degree of polymerization (30-350 determined indirectly via UV spectrometry). The systems used for separation and characterization of branched polysaccharides were SEC-DMSO/LiBr and multi detection (refractive index detector, viscosity detector, and multi angle light scattering detector) and SEC-water/0.02% NaN(3); and SEC-50 mM NaNO(3)/0.02% NaN(3) and multi detection. Additionally the side chain length distribution of enzymatically debranched polysaccharides was investigated by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) analysis. With this combination of characterization techniques, we were able not only to characterize the amylopectin analogues but also to solve parts of the molecular mechanism of their enzymatic polymerization. Moreover our materials showed potential to be standards in the field of natural polysaccharides characterization.

Environmentally benign synthesis of saturated and unsaturated aliphatic polyesters via enzymatic polymerization of biobased monomers derived from renewable resources

Aliphatic polyesters are of great interest due to their broad potential applications and sustainability. Itaconate-based aliphatic polyesters are even more appealing in biomedical and pharmaceutical fields, as they are renewable functional polymers that can be biodegradable, biocompatible, and photo-curable, and might be bioresorbable. Herein, various biobased saturated aliphatic polyesters and itaconate-based unsaturated aliphatic polyesters are successfully produced via Candida antarctica Lipase B (CALB)-catalyzed polycondensation of (potentially) biobased dimethyl itaconate, 1,4-butanediol and various diacid ethyl esters, using a two-stage method in diphenyl ether. The synthetic aliphatic polyesters reach high (weight average molecular weight) values up to 94 kg mol−1. Studies on the effect of diacid ethyl esters on the enzymatic polymerization reveal that CALB prefers diacid ethyl esters having a chain length of more than 2 (n > 2, n is the number of methylene groups between the two carbonyl groups); and CALB shows the highest specificity for diethyl adipate among the tested diacid ethyl esters (n = 2–10). Moreover, the structure–property relationships are discussed by investigating the chemical structures, crystalline properties and thermal properties of the obtained aliphatic polyesters, as well as, the thermal transitions and mechanical properties of the UV cross-linked unsaturated polyesters.

Tunable Properties of Inclusion Complexes Between Amylose and Polytetrahydrofuran

Amylose and polytetrahydrofuran (PTHF) are mixed in an aqueous solution to form inclusion complexes. DSC shows that immediate mixing results in complexes having lower melting temperatures compared with complexes prepared with longer mixing times. The washed complexes melt at higher temperatures compared with the corresponding unwashed complexes. XRD indicates that amylose-PTHF complexes diffract similar to amylose-fatty acids complexes (V6I -amylose helices), with additional diffractions correlating with amylose-alcohol complexes (V6II -amylose helices). This suggests that the structure of amylose-PTHF complexes is an intermediate or a mixture between V6I - and V6II -amylose. This shows that, besides residing inside the amylose helices, some PTHF chains are located in between the amylose helices.

Synthesis of Amylose−Polystyrene Inclusion Complexes by a Facile Preparation Route

The formation of amylose-polystyrene inclusion complexes via a novel two-step approach is described. In the first-step, styrene was inserted inside the amylose helical cavity, followed by free radical polymerization in the second step. The inclusion complexes were characterized by attenuated total reflection fourier transform infrared spectroscopy (ATR-FTIR), ultraviolet spectroscopy (UV), X-ray diffraction (XRD), atomic force microscopy (AFM), and differential scanning calorimetry (DSC). The formation of polystyrene was confirmed by gel permeation chromatography (GPC). The molecular weight of polystyrene can be varied by using amylose bearing different molar masses. The approach described here is general and could be used to synthesize other host-polymer inclusion complexes for which long chains of polymeric guests are difficult to insert into the host cavity.

Enzymatic Polymerization of Furan-2,5-Dicarboxylic Acid-Based Furanic-Aliphatic Polyamides as Sustainable Alternatives to Polyphthalamides

Furan-2,5-dicarboxylic acid (FDCA)-based furanic-aliphatic polyamides can be used as promising sustainable alternatives to polyphthalamides (semiaromatic polyamides) and be applied as high performance materials with great commercial interest. In this study, poly(octamethylene furanamide) (PA8F), an analog to poly(octamethylene terephthalamide) (PA8T), is successfully produced via Novozym 435 (N435)-catalyzed polymerization, using a one-stage method in toluene and a temperature-varied two-stage method in diphenyl ether, respectively. The enzymatic polymerization results in PA8F with high weight-average molecular weight (M̅(w)) up to 54000 g/mol. Studies on the one-stage enzymatic polymerization in toluene indicate that the molecular weights of PA8F increase significantly with the concentration of N435; with an optimal reaction temperature of 90 °C. The temperature-varied, two-stage enzymatic polymerization in diphenyl ether yields PA8F with higher molecular weights, as compared to the one-stage procedure, at higher reaction temperatures. MALDI-ToF MS analysis suggests that eight end groups are present in the obtained PA8F: ester/amine, ester/ester, amine/amine, acid/amine, ester/acid, acid/acid, ester/amide, and no end groups (cyclic). Compared to PA8T, the obtained PA8F possesses a similar Tg and similar crystal structures, a comparable Td, but a lower Tm.