Exploiting thermally-reversible covalent bonds for the controlled release of microencapsulated isocyanate crosslinkers

Abstract

The paper reports the successful synthesis of microcapsules that incorporate thermally-reversible Diels-Alder or oxime-urethane bonds within the polymer of the microcapsule shell using an interfacial polymerisation technique. The mechanical strength of these microcapsules was found to be dependent on the structure of the thermally-reversible functionality, thus allowing for the design of strong microcapsules that demonstrated excellent stability in one-pot PU formulations. Release of the encapsulated isocyanate crosslinkers using a thermal stimulus demonstrated the potential of this technology for use in the controlled polymerisation of one-pot PU systems.

Diels–Alder Cycloadditions of Bio-Derived Furans with Maleimides as a Sustainable «Click» Approach towards Molecular, Macromolecular and Hybrid Systems

“…An alternative strategy for the synthesis of CANs with a high degree of cross-linking is the application of bifunctional fmDA adducts for the synthesis of linear or cross-linked pre-polymers [115][116][117], or as co-monomers [47,104,118]. Recently reported representative examples of the bifunctional adducts and types of obtained CANs are presented in Table 5.…”

Experimental characterisation and modelling of the strain rate dependent mechanical response of a filled thermo-reversible supramolecular polyurethane

“…The overall mechanical properties of the composite can depend on the filler size [20,21], filler shape [22,23], filler distribution, alignment [24][25][26], geometric orientation [24], and interfacial adhesion between filler and matrix [27][28][29][30][31]. Another purpose of mixing particulates in a soft polymer is to take advantage of the filler's functionality; for example, in polymer bonded explosives or propellants [32][33][34], where the role of the polymer binder is to make the explosive system more resilient and less sensitive during processing and transportation [35][36][37][38].…”

pH-Triggered Release of NaNO2 Corrosion Inhibitors from Novel Colophony Microcapsules in Simulated Concrete Pore Solution

“…Microencapsulation is an emerging trend in corrosion inhibiting materials, including self-healing coatings, which are developed using microcapsules containing coating healing agents. − Microcapsules have been shown to be effective delivery systems in a variety of applications using many different stimuli including ionic, mechanical, thermal, photic, and pH. − The use of pH-triggered microcapsules containing corrosion inhibitors has been investigated by Gelling et al , in which a microcapsule containing cerium nitrate was encapsulated and the release was studied for protection of aluminum alloys. , The outer shell of a pH-sensitive microcapsule plays an important role in its synthesis and release performance in application. Panda et al have studied colophony applications in the pharmaceutical industry as an encapsulating agent for controlled drug release; colophony consists mainly of abietic acid amongst other resin acids and terpenes. , The porosity of colophony lends itself to be a practical vehicle for inhibitor release as the OH – ions present in the concrete pore solution will react with the colophony resin and the porosity will increase further, allowing the evacuation of the inhibiting agent.…”