Significantly increased production of biobased polymers is aprerequisite to replace petroleum-based materials towardsreaching a circular bioeconomy. However, many renewablebuilding blocks from wood and other plant material are notdirectly amenable for polymerization, due to their inert backbonesand/or lack of functional group compatibility with thedesired polymerization type. Based on a retro-biosyntheticanalysis of polyesters, a chemoenzymatic route from (@)-apinenetowards a verbanone-based lactone, which is furtherused in ring-opening polymerization, is presented. Generatedpinene-derived polyesters showed elevated degradation andglass transition temperatures, compared with poly(e-decalactone),which lacks a ring structure in its backbone. Semirationalenzyme engineering of the cyclohexanone monooxygenasefrom Acinetobacter calcoaceticus enabled the biosynthesis ofthe key lactone intermediate for the targeted polyester. As aproof of principle, one enzyme variant identified from screeningin a microtiter plate was used in biocatalytic upscaling,which afforded the bicyclic lactone in 39% conversion in shakeflask scale reactions.

An all-water-based procedure for "controlled" polymer grafting from cellulose nanofibrils is reported. Polymers and copolymers of poly(ethylene glycol) methyl ether methacrylate (POEGMA) and poly(methyl methacrylate) (PMMA) were synthesized by surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (SI-ARGET ATRP) from the cellulose nanofibril (CNF) surface in water. A macroinitiator was electrostatically immobilized to the CNF surface, and its amphiphilic nature enabled polymerizations of both hydrophobic and hydrophilic monomers in water. The electrostatic interactions between the macroinitiator and the CNF surface were studied by quartz crystal microbalance with dissipation energy (QCM-D) and showed the formation of a rigid adsorbed layer, which did not desorb upon washing, corroborating the anticipated electrostatic interactions. Polymerizations were conducted from dispersed modified CNFs as well as from preformed modified CNF aerogels soaked in water. The polymerizations yielded matrix-free composite materials with a CNF content of approximately 1-2 and 3-6 wt % for dispersion-initiated and aerogel-initiated CNFs, respectively.

Promising electrical field grading materials (FGMs) for high-voltage direct-current (HVDC) applications have been designed by dispersing reduced graphene oxide (rGO) grafted with relatively short chains of poly (n-butyl methacrylate) (PBMA) in a poly(ethylene-co-butyl acrylate) (EBA) matrix. All rGO-PBMA composites with a filler fraction above 3 vol.% exhibited a distinct non-linear resistivity with increasing electric field; and it was confirmed that the resistivity could be tailored by changing the PBMA graft length or the rGO filler fraction. A combined image analysis- and Monte-Carlo simulation strategy revealed that the addition of PBMA grafts improved the enthalpic solubility of rGO in EBA; resulting in improved particle dispersion and more controlled flake-to-flake distances. The addition of rGO and rGO-PBMAs increased the modulus of the materials up to 200% and the strain did not vary significantly as compared to that of the reference matrix for the rGO-PBMA-2 vol.% composites; indicating that the interphase between the rGO and EBA was subsequently improved. The new composites have comparable electrical properties as today's commercial FGMs; but are lighter and less brittle due to a lower filler fraction of semi-conductive particles (3 vol.% instead of 30-40 vol.%).

Sobrerol methacrylate (SobMA) was synthesized and subsequently polymerized using different chemical and enzymatic routes. Sobrerol was enzymatically converted from -pinene in a small model scale by a Cytochrome P450 mutant from Bacillus megaterium. Conversion of sobrerol into SobMA was performed using both classical ester synthesis, i.e., acid chloride-reactions in organic solvents, and a more green approach, the benign lipase catalysis. Sobrerol was successfully esterified, leaving the tertiary alcohol and ene to be used for further chemistry. SobMA was polymerized into PSobMA using different radical polymerization techniques, including free radical (FR), controlled procedures (Reversible Addition Fragmentation chain-Transfer polymerization, (RAFT) and Atom Transfer Radical Polymerization (ATRP)) as well as by enzyme catalysis (horseradish peroxidase-mediated free radical polymerization). The resulting polymers showed high glass-transition temperatures (T-g) around 150 degrees C, and a thermal degradation onset above 200 degrees C. It was demonstrated that the T-g could be tailored by copolymerizing SobMa with appropriate methacrylate monomers and that the Flory-Fox equation could be used to predict the T-g. The versatility of PSobMA was further demonstrated by forming crosslinked thin films, either using the ene'-functionality for photochemically initiated thiol-ene'-chemistry, or reacting the tertiary hydroxyl-group with hexamethoxymethylmelamine, as readily used for thermally curing coatings systems.

This work demonstrates a versatile and environmentally friendly route for the development of new orthogonal monomers that can be used for postfunctionalizable polymer networks. A monomer containing both vinyl ether (VE) and cyclic disulfide moieties was synthesized via enzyme catalysis under benign reaction conditions. The bifunctional monomer could be polymerized to form macromolecues with differing architectures by the use of either cationic or radical photo polymerization. When cationic polymerization was performed, a linear polymer was obtained with pendant disulfide units in the side chain, whereas in the presence of radical initiator, the VE reacted with the disulfide to yield a branched structure. The monomer was thereafter used to design networks that could be postfunctionalized; the monomer was cross-linked with cationic initiation together with a difunctional VE oligomer and after cross-linking the unreacted disulfides were coupled to RhodamineVE by radical UV-initiation.

A molecularly engineered water-borne reactive compatibilizer is designed for tuning of the interface in melt-processed thermoplastic poly(caprolactone) (PCL)-cellulose nanocomposites. The mechanical properties of the nanocomposites are studied by tensile testing and dynamic mechanical analysis. The reactive compatibilizer is a statistical copolymer of 2-(dimethylamino)ethyl methacrylate and 2-hydroxy methacrylate, which is subsequently esterified and quaternized. Quaternized ammonium groups in the reactive compatibilizer electrostatically match the negative surface charge of cellulose nanofibrils (CNFs). This results in core-shell CNFs with a thin uniform coating of the compatibilizer. This promotes the dispersion of CNFs in the PCL matrix, as concluded from high-resolution scanning electron microscopy and atomic force microscopy. Moreover, the compatibilizer "shell" has methacrylate functionalities, which allow for radical reactions during processing and links covalently with PCL. Compared to the bio-nanocomposite reference, the reactive compatibilizer (<4 wt %) increased Young's modulus by about 80% and work to fracture 10 times. Doubling the amount of peroxide caused further improved mechanical properties, in support of effects from higher cross-link density at the interface. Further studies of interfacial design in specific nanocellulose-based composite materials are warranted since the detrimental effects from CNFs agglomeration may have been underestimated.