Abstract
New amphiphilic liquid crystal (LC) polycarbonate block copolymers containing side-chain cholesteryl units were synthesized. Their structure, thermal stability, and LC phase behavior were characterized with Fourier transform infrared (FT-IR) spectrum, 1H NMR, gel permeation chromatographic (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), polarizing optical microscope (POM), and XRD methods. The results demonstrated that the LC copolymers showed a double molecular arrangement of a smectic A phase at room temperature. With the elevating of LC unit content in such LC copolymers, the corresponding properties including decomposition temperature (Td), glass temperature (Tg), and isotropic temperature (Ti) increased. The LC copolymers showed pH-responsive self-assembly behavior under the weakly acidic condition, and with more side-chain LC units, the self-assembly process was faster, and the formed particle size was smaller. It indicated that the self-assembly driving force was derived from the orientational ability of LC. The particle size and morphologies of self-assembled microspheres loaded with doxorubicin (DOX), together with drug release tracking, were evaluated by dynamic light scattering (DLS), SEM, and UV–vis spectroscopy. The results showed that DOX could be quickly released in a weakly acidic environment due to the pH response of the self-assembled microspheres. This would offer a new strategy for drug delivery in clinic applications.
Highlights
Biodegradable aliphatic polyesters have received more and more attention in recent years due to their good biodegradability and biocompatibility [1,2]
Another important point is that liquid crystal (LC) can self-assemble to form a variety of ordered structures which are responsive to temperature, pH, stress, magnetic field, and other external conditions [12,13,14]; as a result, LC structures present considerable advantages in the transport and delivery of diverse active molecules and drugs [15]
It has been reported that the cholesteryl groups could be employed as mesogenic units to fabricate side-chain [19,20,21,22,23] and main-chain LC polymers [24,25,26,27,28]
Summary
Biodegradable aliphatic polyesters have received more and more attention in recent years due to their good biodegradability and biocompatibility [1,2]. Four class of polyesters, namely polyglycolide (PGA), poly(1,3-trimethylene carbonate) (PTMC), polylactide (PLA), poly(caprolactone) (PCL), and their copolymers, are the most widely studied and utilized in biomedical fields. Exploration of their applications has been hampered by several limitations owing to their specific properties, for example, the PGA degradation rate is too fast with respect to the required application time of materials [3,4,5]; and PLA can produce acid degradation products which may cause aseptic inflammation [6]. There is limited research on aliphatic polycarbonates with side-chain cholesteryl LC units [21,29]
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