Controlled Synthesis and Crystallization-Driven Self-Assembly of Poly(<i>ε</i>-caprolactone)-<i>b</i>-polysarcosine Block Copolymers
Poly(ε-caprolactone)-<i>b</i>-polysarcosine (PCL-<i>b</i>-PSar) block copolymers (BCPs) emerge as a promising alternative to conventional poly(<i>ε</i>-caprolactone)-<i>b</i>-poly(ethylene oxide) BCPs for biomedical applications, leveraging superior bi...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-07-01
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| Series: | Molecules |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1420-3049/30/15/3108 |
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| Summary: | Poly(ε-caprolactone)-<i>b</i>-polysarcosine (PCL-<i>b</i>-PSar) block copolymers (BCPs) emerge as a promising alternative to conventional poly(<i>ε</i>-caprolactone)-<i>b</i>-poly(ethylene oxide) BCPs for biomedical applications, leveraging superior biocompatibility and biodegradability. In this study, we synthesized two series of PCL-<i>b</i>-PSar BCPs with controlled polymerization degrees (<i>DP</i> of PCL: 45/67; <i>DP</i> of PSar: 28–99) and low polydispersity indexes (<i>Đ</i> ≤ 1.1) and systematically investigated their crystallization-driven self-assembly (CDSA) in alcohol solvents (ethanol, <i>n</i>-butanol, and <i>n</i>-hexanol). It was found that the limited solubility of PSar in alcohols resulted in competition between micellization and crystallization during self-assembly of PCL-<i>b</i>-PSar, and thus coexistence of lamellae and spherical micelles. To overcome this morphological heterogeneity, we developed a modified self-seeding method by employing a two-step crystallization strategy (i.e., <i>T</i><sub>c1</sub> = 33 °C and <i>T</i><sub>c2</sub> = 8 °C), achieving conversion of micelles into crystals and yielding uniform self-assembled structures. PCL-<i>b</i>-PSar BCPs with short PSar blocks tended to form well-defined two-dimensional lamellar crystals, while those with long PSar blocks induced formation of hierarchical structures in the PCL<sub>45</sub> series and polymer aggregation on crystal surfaces in the PCL<sub>67</sub> series. Solvent quality notably influenced the self-assembly pathways of PCL<sub>45</sub>-<i>b</i>-PSar<sub>28</sub>. Lamellar crystals were formed in ethanol and <i>n</i>-butanol, but micrometer-scale dendritic aggregates were generated in <i>n</i>-hexanol, primarily due to a significant Hansen solubility parameter mismatch. This study elucidated the CDSA mechanism of PCL-<i>b</i>-PSar in alcohols, enabling precise structural control for biomedical applications. |
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| ISSN: | 1420-3049 |