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.

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Biocompatible gels based on poly(3-hydroxyalkanoate)s (PHAs) were developed by radical polymerization in the presence of poly(ethylene glycol) diacrylate (PEGDA). In order to elaborate cross-linked networks based on PEGDA and PHAs, several PHAs were tested; saturated PHAs, such as poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) or poly(3-hydroxyoctanoate) (PHO), and an unsaturated PHA, poly(3-hydroxyoctanoate-co-3-hydroxyundecenoate) PHOU. The PHAxPEGDA1-x networks obtained in this work were studied by FTIR, Raman spectroscopy, DSC, TGA and NMR. The microscopic structure varied according to the mass proportions between the two polymers. Time Domain 1H DQ NMR measurements demonstrated that in the case of the unsaturated PHA, it was chemically crosslinked with PEGDA, due to the presence of double bonds in the lateral groups. The organogels were able to swell in organic solvents, such as THF, up to 2000% and in water up to 86%. It was observed by rheological analysis that the stiffness of the networks was dependent on the content of PHA and on the degree of cross-linking. The biocompatible characters of PHOU and PEGDA were not affected by the formation of the networks and these networks had the advantage of being non-cytotoxic to immortalized C2C12 myoblast cells.