Abstract
We report a new and robust strategy toward the development of high-performance pressure sensitive adhesives (PSAs) from chemicals directly obtained from raw biomass deconstruction. A particularly unique and translatable aspect of this work was the use of a monomer obtained from real biomass, as opposed to a model compound or lignin-mimic, to generate well-defined and nanostructure-forming polymers. Herein, poplar wood depolymerization followed by minimal purification steps (filtration and extraction) produced two aromatic compounds, 4-propylsyringol and 4-propylguaiacol, with high purity and yield. Efficient functionalization of those aromatic compounds with either acrylate or methacrylate groups generated monomers that could be easily polymerized by a scalable reversible addition–fragmentation chain-transfer (RAFT) process to yield polymeric materials with high glass transition temperatures and robust thermal stabilities, especially relative to other potentially biobased alternatives. These lignin-derived compounds were used as a major component in low-dispersity triblock polymers composed of 4-propylsyringyl acrylate and n-butyl acrylate (also can be biobased). The resulting PSAs exhibited excellent adhesion to stainless steel without the addition of any tackifier or plasticizer. The 180° peel forces were up to 4 N cm–1, and tack forces were up to 2.5 N cm–1, competitive with commercial Fisherbrand labeling tape and Scotch Magic tape, demonstrating the practical significance of our biomass-derived materials.
Highlights
A major component in lignocellulosic biomass, is the most abundant source of aromatic building blocks in nature,[1] and the depolymerization of lignin is capable of producing value-added small aromatic molecules with great potential as fuel additives and platform chemicals.[2−8] the aromatic moieties in lignin are linked by various kinds of robust C−C and C−O bonds,[9] and deconstruction of lignin generates a complex mixture of disparate compounds.[4,10−14] Few studies have focused on the direct use of chemicals from raw biomass deconstruction.[15,16]
Lignin model compounds have been extensively explored toward the formulation of new products for applications, such as thermoplastics, thermoplastic elastomers, coatings, pressure sensitive adhesives (PSAs), composites, and resins.[17−26] a major unanswered question is “Can these biobased compounds be harvested from raw biomass to produce designer materials in a scalable and cost-effective manner?” Essentially, a huge gap exists between deriving well-defined chemicals from raw biomass and directly utilizing these chemicals for the formulation of specialized consumer products
To demonstrate the ease of producing model consumer products directly from raw biomass depolymerization products, a triblock polymer was synthesized with poly(4-propylsyringyl acrylate) (P4pSA) as the glassy end blocks and poly(n-butyl acrylate) (PBA) as the midblock, generating poly(4pSA-bBA-b-4-Propylsyringyl Acrylate (4pSA)) (SaBSa) (Scheme 1 step 3, details are located in the Methods section and the SI)
Summary
A major component in lignocellulosic biomass, is the most abundant source of aromatic building blocks in nature,[1] and the depolymerization of lignin is capable of producing value-added small aromatic molecules with great potential as fuel additives and platform chemicals.[2−8] the aromatic moieties in lignin are linked by various kinds of robust C−C and C−O bonds,[9] and deconstruction of lignin generates a complex mixture of disparate compounds (monophenols, dimers, and oligomers).[4,10−14] Few studies have focused on the direct use of chemicals from raw biomass deconstruction.[15,16] Instead, lignin model compounds have been extensively explored toward the formulation of new products for applications, such as thermoplastics, thermoplastic elastomers, coatings, pressure sensitive adhesives (PSAs), composites, and resins.[17−26] a major unanswered question is “Can these biobased compounds be harvested from raw biomass to produce designer materials in a scalable and cost-effective manner?” Essentially, a huge gap exists between deriving well-defined chemicals from raw biomass and directly utilizing these chemicals for the formulation of specialized consumer products. Rubbery segment-miscible tackifiers or plasticizers often are blended with these PI- or PB-based block polymers to lower the material’s storage modulus and enhance adhesion with the substrate.[28] Acrylate-based block polymers, such as those containing glassy poly(methyl methacrylate) (PMMA) end blocks with a rubbery poly(n-butyl acrylate) (PBA) middle block, typically exhibit good adhesion with and without tackifier additives because of the lower effective modulus,[35] and much higher Me (Me = 28 kg mol−1) of the PBA block.[36] n-butyl acrylate is an attractive choice as it can be derived from biosourced n-butanol.[37] if the PMMA can be replaced by a renewable and sustainable component,[38,39] it will be possible to realize fully sustainable PSAs, as will be demonstrated
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