Enzymatic surface modification and functionalization of PET: A water contact angle, FTIR, and fluorescence spectroscopy study

Abstract

The purpose of this study was to investigate the changes induced by a lypolytic enzyme on the surface properties of polyethylene terephthalate (PET). Changes in surface hydrophilicity were monitored by means of water contact angle (WCA) measurements. Fourier Transform Infrared spectroscopy (FTIR) in the Attenuated Total Reflectance mode (ATR) was used to investigate the structural and conformational changes of the ethylene glycol and benzene moieties of PET. Amorphous and crystalline PET membranes were used as substrate. The lipolytic enzyme displayed higher hydrolytic activity towards the amorphous PET substrate, as demonstrated by the decrease of the WCA values. Minor changes were observed on the crystalline PET membrane. The effect of enzyme adhesion was addressed by applying a protease after-treatment which was able to remove the residual enzyme protein adhering to the surface of PET, as demonstrated by the behavior of WCA values. Significant spectral changes were observed by FTIR-ATR analysis in the spectral regions characteristic of the crystalline and amorphous PET domains. The intensity of the crystalline marker bands increased while that of the amorphous ones decreased. Accordingly, the crystallinity indexes calculated as band intensity ratios (1,341/1,410 cm(-1) and 1,120/1,100 cm(-1)) increased. Finally, the free carboxyl groups formed at the surface of PET by enzyme hydrolysis were esterified with a fluorescent alkyl bromide, 2-(bromomethyl)naphthalene (BrNP). WCA measurements confirmed that the reaction proceeded effectively. The fluorescence results indicate that the enzymatically treated PET films are more reactive towards BrNP. FTIR analysis showed that the surface of BrNP-modified PET acquired a more crystalline character.

Nature Inspired Solutions for Polymers: Will Cutinase Enzymes Make Polyesters and Polyamides Greener?

“…The validity of such an approach was further confirmed by other mutagenesis experiments where the regions in proximity to the active site of cutinases from Thermobifida fusca and from Fusarium solani pisi were mutated for changing the superficial hydrophobicity: mutants turned out to have improved PET hydrolytic performances [82,83]. Other cutinases able to perform PET hydrolysis are those from Humicola insolens, Thielavia terrestris, Pseudomonas mendocina, and Penicillum citrinum [69,74]. Notably, Humicola insolens cutinase demonstrated high hydrolytic activity due to its stability after prolonged incubation at 70 • C, which corresponds to an optimal hydrolysis temperature, being very close to the T g of PET.…”

“…On the other hand, the ability of enzymes to hydrolyze polymers can be exploited for structural fine-tuning and for controlling the degree of polymer functionalization by operating under mild conditions [57]. The possibility to perform partial hydrolysis on the outer layer of the polymer can be exploited for changing the superficial properties in terms of hydrophobicity/hydrophilicity balance, obtaining reactive groups for successive modifications, and changing the polymer biocompatibility just to name a few [68][69][70].…”

Role of Biotechnology in the Treatment of Polyester Fabric

“…Action of lipase in the presence of Triton-X-100 resulted in the formation of novel polar groups that enhanced the dyeability to as much as 130% for cutinase and 300% in the case of lipase. In a study performed by Donelli et al [44] enzymatic surface modification of polyethylene terephthalate was carried out and studies were carried out to determine the water contact angle, FTIR and fluorescence spectroscopy.…”

Advanced microgel-functionalized polyester textiles adaptive to ambient conditions

“…Also, in the region 1400-1700 cm -1 bands of increased absorbance are observed for PET RCM 1, compared with reference PET R 1. In this spectral region, polyester absorbs due to its benzene rings (ring C-H bending, and stretching of the C-C bond between the benzene ring and the carbonyl group) (Liang et al 1959;Donelli et al 2009). However, the stronger bands of PET RCM 1 indicate the presence of amide groups on the polyester surface, which are, therefore, assigned to microgel CM based on Figure 2.8.…”

“…However, in search of "greener" technologies, plasma techniques in all variations of gas type, power etc. (Gouveia et al 2011;Lei et al 2011;Lopez-Santos et al 2010;Parvinzadeh et al 2011) seem to be preferred, while enzymatic treatments (Akkaya et al 2011;Donelli et al 2009;Kardas et al 2011) are gaining interest. Furthermore, the attention for functionalization has shifted in the recent years towards localized modifications, such as photo-grafting or immobilization of functional groups and polymers on specific reactive sites of the substrate (Ito et al 2007;Vladkova 2010).…”