Supramolecular Cross-Links in Poly(alkyl methacrylate) Copolymers and Their Impact on the Mechanical and Reversible Adhesive Properties

Abstract

Hydrogen-bonded, side-chain-functionalized supramolecular poly(alkyl methacrylate)s were investigated as light- and temperature-responsive reversible adhesives that are useful for bonding and debonding on demand applications. Here, 2-hydroxyethyl methacrylate (HEMA) was functionalized with 2-ureido-4[1H]pyrimidinone (UPy) via a hexamethylenediisocyanate (HMDI) linker, to create a monomer (UPy-HMDI-HEMA) that serves to form supramolecular cross-links by way of forming quadruple hydrogen bonded dimers. UPy-HMDI-HEMA was copolymerized with either hexyl methacrylate or butyl methacrylate to create copolymers comprising 2.5, 5, or 10 mol % of the cross-linker. The mechanical properties of all (co)polymers were investigated with stress-strain experiments and dynamic mechanical analysis. Furthermore, the adhesive properties were studied at temperatures between 20 and 60 °C by testing single lap joints formed with stainless steel substrates. It was found that increasing the concentration of the UPy-HMDI-HEMA cross-linker leads to improved mechanical and adhesive properties at elevated temperatures. Concurrently, the reversibility of the bond formation remained unaffected, where rebonded samples displayed the same adhesive strength as regularly bonded samples. Debonding on demand abilities were also tested exemplarily for one copolymer, which for light-induced debonding experiments was blended with a UV-absorber that served as light-heat converter. Single lap joints were subjected to a constant force and heated or irradiated with UV light until debonding occurred. The necessary debonding temperature was comparable for direct heating and UV irradiation and varied between 28 and 82 °C, depending on the applied force. The latter also influenced the debonding time, which under the chosen conditions ranged from 30 s to 12 min.

Pressure-sensitive adhesive utilizing molecular interactions between thymine and adenine

“…The values of strain at break point were 42.8 (60 mol % of adenine moieties of 2 ) and 12.7 (100 mol %), while the sample was not broken and extended to the measurement limit in the case of 30 mol % of adenine moieties of 2 . These results indicate that hydrogen bonding between thymine and adenine units contributes strongly to the mechanical properties of the PSA samples . Similar stress–strain curves were also recorded with samples of copolymers of different molecular weights.…”

“…PSAs utilizing noncovalent interactions have recently been reported where reversible polymer networks are formed. Weder et al reported adhesive materials consisting of polymers having Upy or Mebip moieties, where multiple hydrogen or co‐ordination bonds are formed between the moieties . Zimmerman et al reported adhesive materials utilizing noncovalent interactions between nucleobase analog units .…”

Supramolecular polymer adhesives: advanced materials inspired by nature

“…53 The resulting material displays polymer-like mechanical properties (tensile storage modulus E 0 = 7.1 AE 1.8 MPa, Young's modulus E = 12 AE 1 MPa; measured at 25 1C, respectively) on account of its nanophase segregated lamellar morphology, in which the stacks formed by aggregating UPy dimers serve as the hard phase. 52 Thus, 2-hydroxyethyl methacrylate (HEMA) was functionalized with ureido-4-pyrimidinone (UPy) via a hexamethylenediisocyanate (HMDI) linker. Such functionality can be enabled through a light-heat conversion process whereby the UV-absorbing groups absorb UV light and produce a temperature increase on account of radiationless decay of the excited states.…”

Oleic acid‐based poly(alkyl methacrylate) as bio‐based viscosity control additive for mineral and vegetable oils

“…For instance, poly(alkyl (meth)acrylate)s (PAMAs) have been widely used since the beginning of the 20th century and constitute one of the most important family of polymers obtained by radical polymerization . The widespread use of PAMAs is attributed to their high versatility allowing them to meet a wide range of applications such as adhesives [ ], waterborne coatings , and more particularly as additives for lubricating oils . Indeed, PAMAs have the ability to considerably reduce the viscosity‐temperature dependency of mineral oils .…”