Abstract
A novel generation of gels based on medium chain length poly(3-hydroxyalkanoate)s, mcl-PHAs, were developed by using ionic interactions. First, water soluble mcl-PHAs containing sulfonate groups were obtained by thiol-ene reaction in the presence of sodium-3-mercapto-1-ethanesulfonate. Anionic PHAs were physically crosslinked by divalent inorganic cations Ca2+, Ba2+, Mg2+ or by ammonium derivatives of gallic acid GA-N(CH3)3+ or tannic acid TA-N(CH3)3+. The ammonium derivatives were designed through the chemical modification of gallic acid GA or tannic acid TA with glycidyl trimethyl ammonium chloride (GTMA). The results clearly demonstrated that the formation of the networks depends on the nature of the cations. A low viscoelastic network having an elastic around 40 Pa is formed in the presence of Ca2+. Although the gel formation is not possible in the presence of GA-N(CH3)3+, the mechanical properties increased in the presence of TA-N(CH3)3+ with an elastic modulus G’ around 4200 Pa. The PHOSO3−/TA-N(CH3)3+ gels having antioxidant activity, due to the presence of tannic acid, remained stable for at least 5 months. Thus, the stability of these novel networks based on PHA encourage their use in the development of active biomaterials.
Highlights
Poly(3-hydroxyalkanoate)s (PHAs) are natural polymers produced by microorganisms as carbon and energy storage compounds when they are placed under special growth conditions
PHAs can be divided into three main types depending on the number of carbon atoms in the monomer unit: short-chainlength PHAs, with monomers consisting of 3–5 carbon atoms, medium-chainlength PHAs, with monomers consisting of 6–14 carbon atoms, and long chain length PHAs, which are obtained from long chain fatty acids with more than 14 carbon atoms
Sulfonate groups were grafted to the terminal double bonds of the PHOU, to both provide an amphiphilic character to the PHA and to induce non-covalent binding of SO3 − ions to cationic species to form ionic crosslinking (Figure 1)
Summary
Poly(3-hydroxyalkanoate)s (PHAs) are natural polymers produced by microorganisms as carbon and energy storage compounds when they are placed under special growth conditions. Soluble PHAs obtained retained their biocompatible and non-cytotoxic character and the presence of PEG introducing PEG [18], ammonium groups [25], or sulfonate functions [26,27] retainedand their propyleneglycol (PPG). PHAs haveasalready been gel via photo-crosslinking based from on a thiol-ene reaction with PEG-dithiol a photo-crossdescribed in the literature, there is from to our knowledge no study on the have gels with. These novel materials should constitute support described in thegroups. The viscoelastic properties of the gels and their antioxidant activity were studied
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