Integrating Mussel Chemistry into a Bio-Based Polymer to Create Degradable Adhesives

Abstract

Adhesives releasing carcinogenic formaldehyde are almost everywhere in our homes and offices. Most of these glues are permanent, preventing disassembly and recycling of the components. New materials are thus needed to bond and debond without releasing reactive pollutants. In order to develop the next generation of advanced adhesives we have turned to biology for inspiration. The bonding chemistry of mussel proteins was combined with preformed poly(lactic acid), a bio-based polymer, by utilizing side reactions of Sn(oct) 2 , to create catechol-containing copolymers. Structure−function studies revealed that bulk adhesion was comparable to that of several petroleum-based commercial glues. Bonds could then be degraded in a controlled fashion, separating substrates gradually using mild hydrolysis conditions. These results show that biomimetic design principles can bring about the next generation of adhesive materials. Such new copolymers may help replace permanent materials with renewable and degradable adhesives that do not create chronic exposure to toxins.

The Chemistry behind Catechol‐Based Adhesion

“…[84,85] Based on this observation, several groups focused on the synthesis of catechol-based adhesive materials with optimised catechol contents. [86][87][88][89][90][91] Mussel-inspired biomimetic polymers have been mainly prepared from polyesters, [88,89] polyamides, [92] polyacrylates, [93][94][95][96] polyethylene glycols, [16,[97][98][99] polyoxetanes, [87,91] polystyrenes [86,100] polypeptides, [101][102][103] and polysaccharides. [104,105] Ther esults defined ar ange for the optimal catechol content close to that observed in mfps,b ut with differences depending on the nature of the material used.…”

High Strength Adhesives from Catechol Cross‐Linking of Zein Protein and Plant Phenolics

“…Prior work with catechol containing polymer systems showed a rise and then decline in adhesion as function of catechol content [23] or polymer type. [33] In other words, there was an optimal composition or maximum in adhesion strength. Here ( Figure 2) the data show enhanced adhesion up to a plateau.…”

“…Even higher concentrations of catechol would come at the expense of zein content and, if similar to prior work, could be expected to decrease adhesion. [23,33,35] [23,33,35] …”

“…[34] Thus the plateau value ( Figure 2) will eventually decrease, depending on the changing adhesives composition. [23,33,35]…”

Strong Adhesives from Corn Protein and Tannic Acid

“…[6] Since bio-based strong adhesives are needed to replace several synthetic products, nontoxic plant polymers derived from renewable resources such as corn or soy have become attractive for research. [10] Tannic acid is a plant-based polyphenol that is well known [11] and generally recognized as safe (GRAS) by the Food and Drug Administration. [11,12] When used for multifunctional crosslinking, tannic acid can provide cohesive strength to polymer networks such as zein, and add adhesive properties that the polymer, by itself, does not have.…”