Catechol-Functionalized Latex Polymers Display Improved Adhesion to Low-Surface-Energy Thermoplastic Polyolefin Substrates

Abstract

We report the synthesis and characterization of catechol-functionalized film-forming latexes that display excellent adhesion to low-surface-energy polyolefin-based substrates. The aromatic 1,2-diol functional group in catechol derivatives is believed to be responsible for enhancing the adhesion of a variety of polymers to a range of substrates. Here, we describe a postpolymerization modification approach to the design of emulsion polymers with catechol-functionalized side chains. A series of analogous small-molecule reactions, together with latex characterization by infrared (IR) spectroscopy and liquid chromatography (LC) methods, provides evidence for polymer functionalization. Films prepared from catechol-containing latexes displayed remarkable adhesion to challenging, commercially-available thermoplastic polyolefin (TPO) (as determined by a standard ASTM cross-hatch method). We provide evidence that covalent bonding and the unique catechol structure are required to promote adhesion. The catechol-functionalized emulsion polymers reported here represent a new class of functional latex, and this postpolymerization modification approach will present further opportunities to improve, modulate, and control the adhesion of water-borne coatings to a variety of polyolefin-based substrates.

Tuning the Lignin-Caprolactone Copolymer for Coating Metal Surfaces

“…Furthermore, we speculate that unreacted phenolic OH or catechol groups that have not been modified by the aliphatic esters contribute to the high adhesion properties. Recently, it has been found that catechol groups covalently functionalize to the latex polymer, stimulating adhesion properties . Overall, it can be said that the pull-off adhesion strength of the lignin-based system is in the range of other commercially available polyester-melamine-based coatings (2-15MPa). − …”

“…Adhesion properties of 20 ± 5 μm thick coatings of steel surfaces were analyzed using a cross-cut tape test (ASTM D3359-97) and a pull-off test (ASTM D4541). 23,43,44 The cross-cut tape test was obtained with an Elcometer 1542 Cross Hatch tester equipped with a multiple-blade cutting wheel with a 1 mm separation. The adhesive tape was placed on the grids and then removed with a firm pulling action.…”

“…Recently, it has been found that catechol groups covalently functionalize to the latex polymer, stimulating adhesion properties. 23 Overall, it can be said that the pull-off adhesion strength of the ligninbased system is in the range of other commercially available polyester-melamine-based coatings (2-15MPa). 67−70…”

“…is an important requirement for polymer coatings . Recently, polymers have been tailored to improve their adhesive properties by taking advantage of mussel adhesive proteins and other compounds rich in catechol functions. − Although lignin has natural adhesive properties because of its phenolic characteristics, its film forming ability remains underdeveloped because of its high glass-transition temperature around 150 °C and low molar mass, which is generally below 5000 g/mol. For this reason, lignin has so far found use in classical coatings mainly as an additive, such as a lignosulfonate-based emulsifier or as an antioxidant. , Because of the inherent limitation, lignin as the main film-forming component has been employed in submicron thicknesses by spin coating, and in such a case, good adhesion to the metal substrate was possible. , To extend lignin utilization as a binder in common coating applications, for example, metal primers applied by spraying, proper film forming with higher thickness levels is needed.…”

Fast-Curing Mussel-Inspired Adhesive Derived from Vegetable Oil

“…These works could be traced back to Messersmith et al’s publication for reversible wet/dry adhesives using catechol-containing poly­(acrylamide-acrylate)-coated nanofabricated polymer pillars . After that, the design of mussel-inspired polymers is under fast growth, and many polymers conjugated with catechol moieties have been reported. ,− Although both synthetic and natural polymers are used as the backbone for mussel-inspired polymers, the former are more widely studied due to their structural abundancy, including but not limited to synthetic polypeptides, , polyols, − polystyrenes, − polyacrylate/amides, ,− hyperbranched polymers, − poly­(urethane-urea)­s, , polyvinyl alcohols, , and polyvinylpyrrolidones. , For example, Deming and Yu reported the synthesis of catechol containing copolypeptides via N -carboxyanhydride polymerization, which exhibited a tensile strength up to 4.0 MPa on aluminum . Becker et al reported the synthesis of amino-acid-based poly­(ester-urea) copolymers with pendant catechol groups via interfacial polycondensation, which exhibited a tensile strength up to 3.5 MPa on aluminum .…”