Liquid crystals are rigid molecules that form ordered phases, and the incorporation of these mesogens into polymeric networks directly links molecular ordering to polymer chain conformation and impacts rubber elasticity. For example, switching between an ordered liquid crystalline phase and the isotropic phase induces changes in polymer chain conformation on the molecular scale, translating into observable shape changes on the macroscale. Because of their anisotropic properties and ability to display shape-morphing behavior, liquid crystalline networks have attracted interest as well-controlled substrates for biological applications. However, most liquid crystalline networks (LCNs) are synthetic networks that lack ligands that cells can recognize. To improve translation of liquid crystalline properties from the network to cells attached to the LCN substrate, the ability to incorporate synthetic peptide chains directly into the network is highly desirable. We have previously reported on the synthesis of LCN films by reacting dialkyne functionalized liquid crystalline monomer (5yH) with diazide terminated polyethylene glycol oligomers (PEG600) and a tetrafunctional azide polyethylene glycol crosslinker (4arm-PEG2k). The networks display sub-ambient glass transitions and shape-morphing properties, including the ability to actuate, which is a reversible extension and contraction of the material. The networks also support the attachment and growth of human mesenchymal stem cells. To increase relevance for biomaterial applications, the incorporation of a novel photoreactive spacer 1,4-cis-butene-bis(azido butanoate) (CBA) is incorporated into the network. The synthesis and design of this CBA spacer provides a bifunctional azide that is capable of incorporating into the alkyne-azide click chemistry polymer network, while also providing an additional reactive site that may be modified by photo-click chemistry (e.g. thiol-ene) to incorporate a desired biological molecule. It is established that this synthesis method has minimal impact on the liquid crystalline properties of the network. Ongoing work is quantifying the amount of peptide incorporation into the network, and the subsequent effects of those modifications on the network’s biological activity. This research seeks to develop a simple platform with a versatile attachment scheme that can be applied to different peptides. Increasing biological interaction with LCNs brings liquid crystalline materials one step closer to broader tissue engineering applications.
