Introducing Amine Functionalities on a Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Surface:  Comparing the Use of Ammonia Plasma Treatment and Ethylenediamine Aminolysis

Abstract

Amine functionalities were introduced onto the surface of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films by applying radio frequency ammonia plasma treatment and wet ethylenediamine treatment. The modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS) for chemical composition and Raman microspectroscopy for the spatial distribution of the chemical moieties. The relative amount of amine functionalities introduced onto the PHBV surface was determined by exposing the treated films to the vapor of trifluoromethylbenzaldehyde (TFBA) prior to XPS analysis. The highest amount of amino groups on the PHBV surface could be introduced by use of ammonia plasma at short treatment times of 5 and 10 s, but no effect of plasma power within the range of 2.5-20 W was observed. Ethylenediamine treatment yielded fewer surface amino groups, and in addition an increase in crystallinity as well as degradation of PHBV was evident from Fourier transform infrared spectroscopy. Raman maps showed that the coverage of amino groups on the PHBV surfaces was patchy with large areas having no amine functionalities.

Surface wettability and energy effects on the biological performance of poly-3-hydroxybutyrate films treated with RF plasma

“…Characteristic amino-related bonds, such as C-N stretching at 1190-1130 cm−1 or N-H (1400-1000 cm−1), were not identified. However, the amino (C-N) and amide (N-C_O) groups on the polymer surface after the ammonia-plasma treatment were identified using X-ray photoelectron spectroscopy [15,17]. Therefore, the FT-IR ATR technique did not provide a clear understanding of the formation of amino, C_O, C-O-C or other groups because only the surface layers of the polymers were modified by the plasma and the information depth of the analysis was in the range of 1-2 μm.…”

“…Radio-frequency (RF) plasma is usually used to treat the surface of different polymers [14,15]. Reactive gases allowus to obtain the necessary functional groups on the P3HB surface and also impart other properties, such as bioactivity [16][17][18][19]. The data on the influence of the different working parameters of plasma, such as the type of gas, power, or pressure, on the changes in the properties of PHA, particularly hydrophilicity, is limited.…”

“…It is known that the surface aging effect can play a significant role, due to the effect of the atmosphere on the surface properties of polymers. In one study [17], the hydrophilic properties of the plasma-treated biodegradable polymers deteriorated over time. Thus, the objective of the present study was to modify thin films of P3HB with a low-temperature radio-frequency (RF) plasma using reactive gases (oxygen and ammonia) to improve the hydrophilic properties of the films by forming polar functional groups.…”

“…The theory of surfacewetting, aswell as contact angle hysteresis is described inmore detail in Ref. [16][17][18].…”

“…1e-f) demonstrated that an increase in the power to 250 W led to the destruction of the surface layers of the ammonia plasma-treated P3HB. It could be caused by hydrogen, which acts as a chemical agent and etches oxygen from the surface [17,27].…”