Design of a Waste Paper‐Derived Chemically ‘Reactive’ and Durable Functional Material with Tailorable Mechanical Property Following an Ambient and Sustainable Chemical Approach

Abstract

Controlled tailoring of mechanical property and wettability is important for designing various functional materials. The integration of these characteristics with waste materials is immensely challenging to achieve, however, it can provide sustainable solutions to combat relevant environmental pollutions and other relevant challenges. Here, the strategic conversion of discarded and valueless waste paper into functional products has been introduced following a catalyst-free chemical approach to tailor both the mechanical property and water wettability at ambient conditions for sustainable waste management and controlling the relevant environmental pollution. In the current design, the controlled and appropriate silanization of waste paper allowed to modulate both the a) porosity and b) compressive modulus of the paper-derived sponges. Further, the association of 1,4conjugate addition reaction between amine and acrylate groups allowed to obtain an unconventional waste paper-derived chemically 'reactive' sponge. The appropriate covalent modification of the residual reactive acrylate groups with selected alkylamines at ambient conditions provided a facile basis to tailor the water wettability from moderate hydrophobicity, adhesive superhydrophobicity to non-adhesive superhydrophobicity. The embedded superhydrophobicity in the waste paper-derived sponge was capable of sustaining large physical deformations, severe physical abrasions, prolonged exposure to harsh aqueous conditions, etc. Further, the waste paper-derived, extremely water-repellent sponges and membranes were successfully extended for proof-ofconcept demonstration of a practically relevant outdoor application, where the repetitive remediation of oil spillages has been demonstrated following both selective absorption (25 times) of oils and gravity-driven filtration-based (50 times) separation of oils from oil/water mixtures at different harsh aqueous scenarios.

Michael Addition Reaction Assisted Derivation of Functional and Durable Superhydrophobic Interfaces

“…Proteins are widely known natural polymers made up of amino acids that consist of a wide range of chemical functionalities which can be strategically exploited for chemical modification. Strategic integration of Michael addition reaction with naturally abundant polymers enabled the development of "reactive" interfaces with tailorable water wettability for applicability in patterned interfaces, 74 oil/water separation, 76,77,79,80 and drug delivery. 78 Shome et al exploited the globular cow protein, i.e., bovine serum albumin, to coat on a fibrous substrate (cotton) to develop physically and chemically robust, three-dimensional superhydrophobicity.…”

“…Eventually, it provided a simple basis to embed hydrophobicity, adhesive superhydrophobicity, and nonadhesive superhydrophobicity, as shown in Figure 8I− In 2021, Shome et al developed waste paper based functional sponges with modulable mechanical property and chemistry to resolve the plaguing environmental issue of oil/water remediation (Figure 8N−R). 80 A binder molecule (Figure 8O) added to waste papers generated a mechanically robust, interconnected porous sponge, wherein (a) the hydroxyl groups of AEPTMS underwent mutual condensation with the hydroxyl groups of cellulose (of paper) and (b) AEPTMS polymerization gave rise to a covalently cross-linked interconnected network imparting robustness as shown in Figure 8P. Varying the concentration of the binder molecule allowed modulation of the Young's modulus of the sponges, which also affected the porosity of the sponges.…”

“…Such characteristics are of utmost importance for realistic and diverse applications of the bioinspired coating. In this regard, the environment-friendly Michael addition reaction between amine and acrylate requiring mild operational conditions would provide a prospective platform to tailor the bioinspired water wettability and other relevant physical properties (Figure )including transparency, mechanical property, porosity, etc.following simple and scalable fabrication processes. − In the past, the catalyst-free Michael addition reaction was successfully extended to produce amplified “reactive” surfaces. , Ford et al studied the ability of growing different nanostructures on selected substrates following the catalyst-free aza-Michael addition reaction between branched polyethylenimine (BPEI) and dipentaerythritol penta-acrylate (5-Acl) that resulted in hyperbranched poly­(ester amines) cross-linked thin films with surface amplified functional groups . In 2012, Bechler et al capitalized on this concept of a nanostructured, “reactive” polymeric film of BPEI/5Acl to construct a relatively thick (∼750 nm) multilayer coating following the layer-by-layer deposition approach .…”

“…To overcome this challenge, the Michael addition reaction between BPEI and 5Acl was employed strategically to achieve rapid and controlled growth of chemically “reactive” nanocomplexes (CRPNCs) in solution phase, instead of on a solid surface. The research group of Manna et al introduced and extended these solution phase CRPNCs for developing porous, three-dimensional superhydrophobic monoliths and flexible polymeric superhydrophobic coatings for applications in oil/water separation, ,,− ,,− ,, drug delivery, ,, patterned interfaces, ,,, etc. The controlled growth of CRPNCs through Michael addition reaction and its strategic postcovalent modifications allowed different durable bioinspired wettabilities to be adoptedincluding controllable adhesive/nonadhesive superhydrophobicity, hydrophilic/superhydrophobic patterns, chemically “reactive” superhydrophobicity, and stimuli-responsive superhydrophobicityfollowing simple and scalable fabrications processes. − The as fabricated chemically “reactive” interfaces with tailorable water wettability exhibited impeccable durability and performance at even chemically harsh and challenging settings.…”

“…The strategic use of the catalyst-free Michael addition reaction allowed the successful modulation of mechanical property, porosity, shrinkage, optical transparency, etc. Natural polymers, ,− paper waste, and small molecules , were also tactfully exploited to develop durable, optically transparent coatings embedded with tailorable water wettability and mechanical property, where the catalyst-free Michael addition reaction between amine and acrylate played a pivotal role.…”