The present work describes the synthesis and characterization of fully biobased soft polymer networks for pressure sensitive adhesives applications. The incorporation of different sugars into fatty-acid-based monomers, made it possible to tailor the viscoelastic properties of the materials. Lipase catalysis allowed to afford monomers with varying hydroxyl content and epoxy-functionalities. Step-growth polymerization catalyzed by DBU resulted in soft-polyester networks through combination of the monomers with a biobased diacid. Rheological and adhesion studies were performed to elucidate the different viscoelastic and adhesive properties of the materials as a function of their composition.

The majority of polyesters and polycarbonates are traditionally synthesized through conventional metal-based catalysis. Although effective, due to environmental concerns, their substitution for other more environmentally friendly alternatives has received increasing interest during the last decades. The search for catalytic systems that also allow milder reaction conditions has been intensified, owing to 30the unwanted side reactions, for example, backbone scissoring, that the metal-based catalysts may cause [1]. In this context, enzymes are anticipated as suitable alternatives [2,3,4,5,6,7,-8]. 

The work herein presented describes the synthesis and polymerization of series of bio-based epoxy resins prepared through lipase catalyzed transesterification. The epoxy-functional polyester resins with various architectures (linear, hi branched, and tetra-branched) were synthesized through condensation of fatty acids derived from epoxidized soybean oil and linseed oil with three different hydroxyl cores under bulk conditions. The selectivity of the lipases toward esterification/transesterification reactions allowed the formation of macromers with up to 12 epoxides in the backbone. The high degree of functionality of the resins resulted in polymer thermosets with T-g values ranging from 25 to over 100 degrees C prepared through cationic polymerization. The determining parameters of the synthesis and the mechanism for the formation of the species were determined through kinetic studies by H-1 NMR, SEC, and molecular modeling studies. The correlation between macromer structure and thermoset properties was studied through real-time FTIR measurements, DSC, and DMA.

The use of enzymes as selective catalysts for processing renewable monomers into added value polymers and materials has received increased attention during the last decade. In the present work Candida antarctica lipase B (CalB) was used as catalyst in one-pot routes to synthesise multifunctional oligoester resins based on an epoxy-functional omega-hydroxy-fatty acid (EFA) extracted from birch bark. The chemoselective enzymatic process resulted in three different EFA-based telechelic oligomers with targeted molecular weights; containing maleimide, methacrylate or oxetane as end-groups, respectively. The enzyme catalysed synthesis of the maleimide and the oxetane telechelic oligomers reached full conversion of monomers (>95%) after 2 h. In the case of methacrylate functional oligomer the EFA monomer reached full conversion (>98%) after 2 h but the integration of the methacrylate moiety took more than 10 h. This was due to a rate limiting reaction path using ethylene glycol dimethacrylate as substrate. The oligomer products were characterised by NMR, MALDI-TOF-MS and SEC.

We present a novel near-ambient-temperature approach to telechelic renewable polyesters by exploiting the unique properties of supercritical CO2 (scCO(2)). Bio-based commercially available monomers have been polymerized and functional telechelic materials with targeted molecular weight prepared by end-capping the chains with molecules containing reactive moieties in a one-pot reaction. The use of scCO(2) as a reaction medium facilitates the effective use of Candida antarctica Lipase B (CaLB) as a catalyst at a temperature as low as 35 degrees C, hence avoiding side reactions, maintaining the end-capper functionality and preserving the enzyme activity. The functionalized polymer products have been characterized by H-1 nuclear magnetic resonance spectroscopy, matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry, gel permeation chromatography and differential scanning calorimetry in order to carefully assess their structural and thermal properties. We demonstrate that telechelic materials can be produced enzymatically at mild temperatures, in a solvent-free system and using renewably sourced monomers without pre-modification, by exploiting the unique properties of scCO(2). The macromolecules we prepare are ideal green precursors that can be further reacted to prepare useful bio-derived films and coatings.

A series of epoxy-functional telechelic oligomers containing oxetane end groups have been synthesized. The precursor monomer, extracted from outer Birch bark, was first polymerized through enzyme-catalyzed esterification to form oligomers having epoxy and/or oxetane groups in the structures. The oligoesters were subsequently crosslinked through cationic polymerization either by epoxy or oxetane homopolymerization or copolymerization when both functionalities were present. A study of the polymerizations of the resins was performed "in situ" using real-time Fourier transform infrared spectroscopy revealing a preferred copolymerization when compared with the homopolymerization. By tailoring the different structures, it was possible to control the final mechanical properties of the networks.

The use of monomers based on natural materials as a future supply of raw materials has gained more interest in the last decade. Sources ranging from wood to plant oils and algae are exploited as alternatives to traditional fossil-based resources for the synthesis of polymeric materials. The use of these raw materials is not only of interest because of its abundance, but also in terms of price, durability, and/or biodegradability. In the present study, a series of resins utilizing a monomer derived from birch bark is prepared. The thermoset resins are formed by reacting an epoxy-functional omega-hydroxy fatty acid with methacrylate monomers using enzyme catalysis to form multifunctional resins via a one-pot synthesis. The derived oligomers are crosslinked through different polymerization routes to produce thermosets with different properties and/or functionalities. This approach allows natural-based resins with tuned functionalities and mechanical and thermal properties to be obtained.