Borate cross-linked graphene oxide–chitosan as robust and high gas barrier films

Abstract

Chitosan (CS) is one of the most promising polymers due to its biocompatibility, biodegradability, and natural abundance. However, its poor mechanical and barrier properties make it difficult to satisfy a wide range of applications. Herein, borate ions, originating from the hydrolysis of sodium tetraborate decahydrate (borax), have been used to crosslink chitosan and graphene oxide (GO) nanocomposites. Chitosan films consisting of 1.0 wt% boron and 1.0 wt% GO exhibit a significant improvement in both the toughness and oxygen barrier properties compared to pristine chitosan. In particular the tensile strength of the samples after thermal treatment increases by ∼160% compared to pristine chitosan, whereas their oxygen permeability reduces by ∼90%. This is ascribed to the chemical crosslinking between chitosan and GO nanoplatelets through borate ions, as well as the formation of a layered morphology with graphene nanoplatelets oriented parallel to the sample surface. The exceptional robust and high gas barrier film has promising application in the packaging industry. The borate-crosslinking chemistry represents the potential strategy for improving properties of other polymer nanocomposites.

2D Nanosheets and Their Composite Membranes for Water, Gas, and Ion Separation

“…The membrane had aC O 2 permeance of 650 GPU (1 GPU = 10 À6 cm 3 (STP) cm À2 s À1 cmHg À1 = 3.3 10 À10 mol m À2 s À1 Pa À1 ) and selectivity of 75 over methane (CO 2 /CH 4 ), which exceeded that of other GO membranes and was even comparable to that of zeolites or ultrathin polymers.Y an et al introduced as mall amount of GO to ac hitosan membrane and followed the crosslinking with borate with at hermal treatment to improve its mechanical and barrier properties.T hey found that only 1.0 wt %e ach of boron and GO in chitosan increased the tensile strength by 160 %a nd the original oxygen permeability was surpassed by 10 %. [48] This was mainly because the GO nanosheets and crosslinked network increased the tortuosity of the pathway for gas transport and decreased the gas diffusion. Yang et al prepared thiourea-crosslinked GO (TU-GO) membranes through af acile hydrothermal self-assembly synthesis by immersing ac eramic support tube in aG Oa nd thiourea solution at 80 8 8Cu nder alkaline conditions (pH 8) which caused covalent crosslinking.…”

2D Nanosheets and Their Composite Membranes for Water, Gas, and Ion Separation

“…introduced a small amount of GO to a chitosan membrane and followed the crosslinking with borate with a thermal treatment to improve its mechanical and barrier properties. They found that only 1.0 wt % each of boron and GO in chitosan increased the tensile strength by 160 % and the original oxygen permeability was surpassed by 10 % . This was mainly because the GO nanosheets and crosslinked network increased the tortuosity of the pathway for gas transport and decreased the gas diffusion.…”

An Injectable, Bifunctional Hydrogel with Photothermal Effects for Tumor Therapy and Bone Regeneration

“…As shown in Figure 2 , the gelation time of borax group (OSA‐CS‐Borax hydrogel) was less than 15 s. After replacing borax with PHA, the formation time increased to approximately 90 s. The shorter gelation time of borax group is related to the following reasons: First, borax is a small molecule when compared to PHA particles and is uniformly dispersed at the molecular level (Figure S2, Supporting Information), and accelerates gel formation. Second, borax improves cross‐linking efficiency by linking hydroxyl groups of two chitosan molecular chains . It should be noted that the introduction of DDP shortened gelation time to within 45 s. This is potentially due to the formation of hydrogen bonds between ammonia groups on DDP and CS, and the ammonia groups on DDP may also interact with OSA to accelerate the gel process.…”