Here we report the synthesis of thermosetting resins from low molar mass Kraft lignin fractions of high functionality, refined by solvent extraction. Such fractions were fully characterized by P NMR, 2D-HSQC NMR, SEC, and DSC in order to obtain a detailed description of the structures. Reactive oxirane moieties were introduced on the lignin backbone under mild reaction conditions and quantified by simpleH NMR analysis. The modified fractions were chemically cross-linked with a flexible polyether diamine ( M ≈ 2000), in order to obtain epoxy thermosets. Epoxies from different lignin fractions, studied by DSC, DMA, tensile tests, and SEM, demonstrated substantial differences in terms of thermo-mechanical properties. For the first time, strong relationships between lignin structures and epoxy properties could be demonstrated. The suggested approach provides unprecedented possibilities to tune network structure and properties of thermosets based on real lignin fractions, rather than model compounds.

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This paper demonstrated the feasibility of conducting an enzymatic ring-opening polymerisation by reactive extrusion (REX) at high shear and temperature conditions. Using immobilized Candida antarctica Lipase B (CALB) as catalyst at temperatures ranging from 90 to 130°C, ω-pentadecalactone (PDL) was converted (>99%) by REX at 60 RPM for 15 min to PPDL with ≥M w 163 000 g mol −1 .The majority of current polymerisation methods use metal catalysts. Residual metal catalysts are often undesirable in materials used for biomedical and electronic applications. 1 Immobilized enzyme-catalysts have been shown to have distinct advantages relative to most metal catalysts including: (1) naturally derived, (2) low toxicity, (3) high chemo-and regioselectivity, (4) activity at relatively low temperatures and (5) no need for strict exclusion of water and oxygen. 2-6 The most commonly employed lipase for enzyme-catalysed ring opening polymerisations (eROP) and polycondensations is the immobilized lipase form of Candida antarctica Lipase B (CALB). Of the many lactonic substrates for which CALB is an active polymerisation catalyst, CALB efficiently catalyses ROP's of larger lactones (e.g. ω-pentadecalactone, PDL). 3 The immobilized CALB catalyst used in ref. 4 and herein is Novozyme 435 (N435). ROP of larger lactones are known to be difficult for many organometallic catalysts because the polymerisations are primarily entropy-driven. 7 Nevertheless, recent progress has resulted in a number of chemical catalysts that successfully convert PDL to high molecular weight polymers. Examples of these catalysts are aluminium salen and terdentate phonoxyimine-amine aluminium. Problems encountered with these catalysts are as follows: (i) synthesis from expensive ligands, (ii) requiring inert reaction conditions (e.g. performed in a glove box) and (iii) the use of solvents. 8,9 The ability of lipases to catalyse ring-opening and condensation polymerisations at relatively low temperatures (e.g. 70-90°C) is advantageous to reduce energy input and to preserve thermally sensitive chemical moieties. However, when high molecular weight polymer synthesis is desired, corresponding diffusional constraints must be overcome by either running reactions at higher temperatures (e.g. 150-220°C), which is generally regarded as not feasible for enzyme-catalysts that denature under such conditions, 10 or by adding solvent. For example, for N435-catalyzed synthesis of high molecular weight (M n > 50 000 g mol −1 ) poly(ω-pentadecalactone), PPDL, and poly(ε-caprolactone, PCL), the viscosity was lowered by the addition of toluene. Subsequently, the final polymer products are obtained by precipitation into a non-solvent such as methanol. 11-13 Solvent-based processes reduce the volumetric productivity of reactions and also require solvent recycling.Reactive extrusion (REX) is an industrially relevant technique because it combines polymerisation and processing into a single step. 14 REX has been used to overcome the aforementioned problems of bulk polymerisations, mai...

Poly­(pentadecalactone)-b-poly­(l-lactide) (PPDL-b-PLLA) diblock copolymers were prepared via the organic catalyzed ring-opening polymerization (ROP) of l-lactide (l-LA) from PPDL macroinitiators using either 1,8-diazabicyclo[5.4.0]­undec-7-ene (DBU) or 1,5,7-triazabicyclo[4.4.0]­dec-5-ene (TBD). Synthesis of PLLA blocks targeting degrees of polymerization (DP) up to 500 were found to yield diblock copolymers with crystalline PPDL and PLLA segments when TBD was used as the catalyst. The synthesis was further improved in a one-pot, two-step process using the same TBD catalyst for the synthesis of both segments. The application of these diblock copolymers as a compatibilizing agents resulted in homogenization of a biobased PLLA/poly­(ω-hydroxytetradecanoate) (90:10) blend upon a melt-process, yielding enhanced material properties.

This work reports the development of a sustainable and green one-step wet-feeding method to prepare tougher and stronger nanocomposites from biodegradable cellulose nanofibrils (CNF)/polycaprolactone (PCL) constituents, compatibilized with reversible addition fragmentation chain transfer-mediated surfactant-free poly(methyl methacrylate) (PMMA) latex nanoparticles. When a PMMA latex is used, a favorable electrostatic interaction between CNF and the latex is obtained, which facilitates mixing of the constituents and hinders CNF agglomeration. The improved dispersion is manifested in significant improvement of mechanical properties compared with the reference material. The tensile tests show much higher modulus (620 MPa) and strength (23 MPa) at 10 wt % CNF content (compared to the neat PCL reference modulus of 240 and 16 MPa strength), while maintaining high level of work to fracture the matrix (7 times higher than the reference nanocomposite without the latex compatibilizer). Rheological analysis showed a strongly increased viscosity as the PMMA latex was added, that is, from a well-dispersed and strongly interacting CNF network in the PCL.

Poly(ε-caprolactone) (PCL) is a ductile thermoplastic, which is biodegradable in the marine environment. Limitations include low strength, petroleum-based origin, and comparably high cost. Cellulose fiber reinforcement is therefore of interest although uniform fiber dispersion is a challenge. In this study, a one-step wet compounding is proposed to validate a sustainable and feasible method to improve the dispersion of the cellulose fibers in hydrophobic polymer matrix as PCL, which showed to be insensitive to the presence of the water during the processing. A comparison between unmodified and acetylated cellulosic wood fibers is made to further assess the net effect of the wet feeding and chemical modification on the biocomposites properties, and the influence of acetylation on fiber structure is reported (ATR-FTIR, XRD). Effects of processing on nanofibrillation, shortening, and dispersion of the cellulose fibers are assessed as well as on PCL molar mass. Mechanical testing, dynamic mechanical thermal analysis, FE-SEM, and X-ray tomography is used to characterize composites. With the addition of 20 wt % cellulosic fibers, the Young's modulus increased from 240 MPa (neat PCL) to 1850 MPa for the biocomposites produced by using the wet feeding strategy, compared to 690 MPa showed for the biocomposites produced using dry feeling. A wet feeding of acetylated cellulosic fibers allowed even a greater increase, with an additional 46% and 248% increase of the ultimate strength and Young's modulus, when compared to wet feeding of the unmodified pulp, respectively.

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Smart multiresponsive bionanocomposites with both humidity- and thermally activated shape-memory effects, based on blends of ethylene-vinyl acetate (EVA) and thermoplastic starch (TPS) are designed. Thermo- and humidity-mechanical cyclic experiments are performed in order to demonstrate the humidity- as well as thermally activated shape memory properties of the starch-based materials. In particular, the induced-crystallization is used in order to thermally activate the EVA shape memory response. The shape memory results of both blends and their nanocomposites reflect the excellent ability to both humidity- and thermally activated recover of the initial shape with values higher than 80 and 90%, respectively.