Hydrogen-Bond-Regulated Platelet Micelles by Crystallization-Driven Self-Assembly and Templated Growth for Poly(ε-Caprolactone) Block Copolymers

Abstract

Living crystallization-driven self-assembly (CDSA) is a powerful approach to tailor nanoparticles with controlled size and spatially defined compositions from amphiphilic crystalline block copolymers (BCPs). However, a variety of external constraints usually make the successful applications of living CDSA difficult. Herein, such constraints arising from strong hydrogen-bond (H-bond) interactions between unimers that lead to the failure of living CDSA are effectively overcome via reduction of the H-bond strength. In particular, by adding a H-bond disruptor trifluoroethanol (TFE), decreasing the unimer concentration, and reducing the corona segment length, the H-bond strength between unimers could be efficiently alleviated, leading to the formation of uniform two-dimensional (2D) platelets with controlled size and block comicelles with spatially defined corona chemistries. Moreover, by selectively anchoring one-dimensional (1D) seeds on the surface of as-prepared 2D block comicelles through H-bond interaction, the epitaxial growth of a crystalline BCP from immobilized 1D seeds on 2D platelets illustrates competitive growth behavior in a spatially confined environment.

Precise Control of Two-Dimensional Platelet Micelles from Biodegradable Poly(p-dioxanone) Block Copolymers by Crystallization-Driven Self-Assembly

“…The seeded growth of the PPDO 22 /PPDO 22 -b -PDMA 133 (1:1, w/w) blend unimer formed abundant spherical micelles in addition to 2D platelet micelles (Figure S18). This result was quite different from the seeded growth behavior of PCL core-forming blend combinations as previously reported by us, where the addition of the blending unimer involving the PCL homopolymer and PCL- b -PDMA (or PCL- b -P4VP) block copolymers (1:1, w/w) to the 1D preformed PCL- b -P4VP seed micelles would allow access to the formation of exclusive 2D platelets with impressive uniformity . Therefore, we believe that these spherical micelles were formed from the fast unimer aggregation of the PPDO 22 homopolymer due to the extremely poor solubility of PPDO 22 in EtOH without tethering the solvophilic segment PDMA.…”

“…This result was quite different from the seeded growth behavior of PCL core-forming blend combinations as previously reported by us, where the addition of the blending unimer involving the PCL homopolymer and PCL-b-PDMA (or PCL-b-P4VP) block copolymers (1:1, w/w) to the 1D preformed PCL-b-P4VP seed micelles would allow access to the formation of exclusive 2D platelets with impressive uniformity. 41 Therefore, we believe that these spherical micelles were formed from the fast unimer aggregation of the PPDO 22 homopolymer due to the extremely poor solubility of PPDO 22 in EtOH without tethering the solvophilic segment 8G). Interestingly, when seeded growth took place at an elevated temperature such as 35 °C, a portion of lozenge platelet micelles with four (110) crystalline planes as the edges were created (Figure 9).…”

“…Subsequent addition of the BCP dissolved in common solvents would allow epitaxial growth on the initial seed micelles, yielding precise size and composition control of 1D or 2D particle micelles. These two approaches have been extensively applied for poly­(ferrocenyldimethylsilane) (PFS) core-forming BCPs as reported by Manners and Winnik − and recently have been extended to other core-forming BCPs involving polyethylene conjugated materials such as oligo­( p -phenylenevinylene) − and poly­(3-thiophene), , and biocompatible/biodegradable materials such as PCL, , PLLA, , and polycarbonate. − …”

The Impact of Soft Segment Crystallization and Cross‐Link Density on the Shape Memory Performance of the PCL‐PTMG/Graphene‐ Based Polyurethane Nanocomposites

“…This behavior alongside the high interfacial energy between these incompatible segments leads to a decline in the crystallites' thermal stability. [57,63] According to Figure 3C, for the tPUs, an intense decline in the T c values of the soft segments from positive temperatures (∼ 10 to 30 °C) to negative values (∼ À 30 to À 10 °C), which is close to its T g values (∼ À 50 °C), has been observed. As it can be seen in Figure 3D and Table 4, the T m values of the polyols have also been suppressed in the thermoset PU structure to a range of about À 6 to 16 � C.…”

“…As the blocks of PCL x and PTMG 2000 tend to segregate, the entropy of the segments close to the bonding point further reduces, which limits their ability to form sTable crystallites. This behavior alongside the high interfacial energy between these incompatible segments leads to a decline in the crystallites’ thermal stability [57,63] …”