Sintered electrospun poly(ɛ‐caprolactone)–poly(ethylene terephthalate) for drug delivery

Electrospinning has the inherent advantage of being able to achieve molecular mixing of polymers having substantially different melting points. Electrospun poly(ɛ‐caprolactone)–poly(ethylene terephthalate) (PCL:PET) capsules are densified by sintering to enable drug encapsulation. Proton and diffusive nuclear magnetic resonance, as well as a selective dissolution, suggest an absence of reaction between the two polymers. Sintering at 100 °C successfully densifies 88.89:11.11 and 75:25 PCL:PET blends. Following sintering, the otherwise dense 75:25 composition retains electrospun features and exhibits some “memory” of its previous state. Sintering increases UTS approximately eightfold versus as‐spun values for 88.89:11.11 and 75:25. Elongation increases sixfold and twofold and modulus 44‐ and 69‐fold for the 75:25 and 88.89:11.11 samples, respectively. Differential scanning calorimetry suggests a postsintering structure of nanoscale PET dispersed in PCL along the original fiber directions. Selective PCL removal from dense blends shows that fibrous characteristics remain. An internal shish–kebab‐like structure is also present in as‐spun 75:25 PCL:PET. Water absorption of hydrophobic oil‐containing capsules is approximately zero after 49 days. In contrast, hydrophilic (HPI) oils allow substantial water uptake. Unsurprisingly, there is no release of a model drug from the hydrophobic carrier. HPI oil provides linear (zero‐order) release inversely proportional to PET from the 88.89:11.11 and 75:25 ratios.