Thermally Fast-Curable, “Sticky” Nanoadhesive for Strong Adhesion on Arbitrary Substrates

Demand of adhesives that are strong but ultrathin with high flexibility, optical transparency, and long-term stability has been rapidly growing recently. Here, we suggest a thermally curable, “sticky” nanoadhesive with outstanding adhesion strength accomplished by single-side deposition of the nanoadhesive on arbitrary substrates. The sticky nanoadhesive is composed of an ionic copolymer film generated from two acrylate monomers with tertiary amine and alkyl halide functionalities, formed by a solvent-free method, initiated chemical vapor deposition (iCVD). Because of the low glass transition temperature (<i>T</i>_g) of the copolymer (−9 °C), the ionic copolymer shows a viscoelastic behavior that makes the adhesive attachable to various substrates, regardless of the substrate materials. Moreover, the copolymer film is thermally curable via a cross-linking reaction between the alkyl halide and tertiary amine functionalities, which substantially increased the adhesion strength of the 500 nm thick nanoadhesive greater than 25 N/25 mm within 5 min of curing at 120 °C. The adhesive thickness can further be reduced to 50 nm to achieve greater than 35 N/25 mm within 30 min at 120 °C. The nanoadhesive layer can form uniform adhesion in a large area substrate (up to 130 × 100 mm²) with the deposition of the adhesive only on one side of the substrates to be laminated. Because of its ultrathin nature, the nanoadhesive is also optically transparent as well as highly flexible, which will play a critical role in fabrication and the lamination of future flexible/wearable devices

Thermally Fast-Curable, “Sticky” Nanoadhesive for Strong Adhesion on Arbitrary Substrates

Demand of adhesives that are strong but ultrathin with high flexibility, optical transparency, and long-term stability has been rapidly growing recently. Here, we suggest a thermally curable, “sticky” nanoadhesive with outstanding adhesion strength accomplished by single-side deposition of the nanoadhesive on arbitrary substrates. The sticky nanoadhesive is composed of an ionic copolymer film generated from two acrylate monomers with tertiary amine and alkyl halide functionalities, formed by a solvent-free method, initiated chemical vapor deposition (iCVD). Because of the low glass transition temperature (<i>T</i>_g) of the copolymer (−9 °C), the ionic copolymer shows a viscoelastic behavior that makes the adhesive attachable to various substrates, regardless of the substrate materials. Moreover, the copolymer film is thermally curable via a cross-linking reaction between the alkyl halide and tertiary amine functionalities, which substantially increased the adhesion strength of the 500 nm thick nanoadhesive greater than 25 N/25 mm within 5 min of curing at 120 °C. The adhesive thickness can further be reduced to 50 nm to achieve greater than 35 N/25 mm within 30 min at 120 °C. The nanoadhesive layer can form uniform adhesion in a large area substrate (up to 130 × 100 mm²) with the deposition of the adhesive only on one side of the substrates to be laminated. Because of its ultrathin nature, the nanoadhesive is also optically transparent as well as highly flexible, which will play a critical role in fabrication and the lamination of future flexible/wearable devices

A Sub-minute Curable Nanoadhesive with High Transparency, Strong Adhesion, and Excellent Flexibility

To achieve adhesion between two arbitrary substrates, a sub-minute curable dry nanoadhesive was devised in a one-step manner. The dry adhesive is composed of a copolymer film containing poly­(glycidyl methacrylate) (pGMA) and poly­(2-(dimethyl­amino)­ethyl methacrylate) (pDMAEMA) segments, where the tertiary amine moiety in pDMAEMA acts as an initiator that triggers the ring-opening reaction of the epoxy ring in pGMA, leading to a self-cross-linking of the epoxide groups in pGMA. Optimization of curing condition resulted in dramatic enhancement of the adhesion strength to values exceeding 250 N/cm² of shear strength and 32.5 N/25 mm of peel strength. Also, strong bonds are observed in various types of substrate materials including glass, latex rubber, Si wafer, and many polymeric films to each other. Moreover, it maintained excellent adhesion against harsh mechanical, thermal, and chemical stresses. The copolymer-based nanoadhesive developed in this study will be highly advantageous for emerging flexible and foldable device applications