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 strengt… Show more
“…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.…”
Section: Resultscontrasting
confidence: 83%
“…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).…”
Section: ■ Introductionmentioning
confidence: 98%
“…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. − …”
Two-dimensional (2D) core–shell nanoparticles
have been
attracting increasing interest due to their wide applications in materials
science. Living crystallization-driven self-assembly (CDSA) is an
ambient temperature, seeded growth method of crystallizable block
copolymers (BCPs) in selective solvents, which has been demonstrated
to be a powerful tool for the creation of one-dimensional (1D)/2D
nanomaterials with precise control over size and compositions. Nevertheless,
the development of an efficient living CDSA approach is a challenge
for the case of semicrystalline poly(p-dioxanone)
(PPDO) as a core-forming block, where the dimensional control is poor.
Herein, we demonstrate that the insufficient size control of 2D PPDO
platelets could be overcome through modulation of solvent compositions
or elevating the crystallization temperatures for PPDO. The possible
mechanism involves an improved unimer solubility that avoids fast
unimer aggregation. As a result, uniform 2D platelet micelles with
a controlled area over a substantial size range are created via epitaxial
growth of the unimer. It is noteworthy that the shape control of 2D
platelet micelles from quasi-square to elongated hexagon to lozenge
shapes can be accessible by regulating the crystallization conditions
such as adding different amounts of cosolvents or crystallization
at an elevated temperature. Meanwhile, spatially defined block comicelles
can be achieved via the seeded growth approach from PPDO core-forming
BCPs with different corona functionalities at elevated temperatures.
The excellent water stability and biocompatibility properties of 2D
PPDO platelet micelles further enable them to have a potential application
as cargo vehicles in the drug delivery field.
“…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.…”
Section: Resultscontrasting
confidence: 83%
“…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).…”
Section: ■ Introductionmentioning
confidence: 98%
“…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. − …”
Two-dimensional (2D) core–shell nanoparticles
have been
attracting increasing interest due to their wide applications in materials
science. Living crystallization-driven self-assembly (CDSA) is an
ambient temperature, seeded growth method of crystallizable block
copolymers (BCPs) in selective solvents, which has been demonstrated
to be a powerful tool for the creation of one-dimensional (1D)/2D
nanomaterials with precise control over size and compositions. Nevertheless,
the development of an efficient living CDSA approach is a challenge
for the case of semicrystalline poly(p-dioxanone)
(PPDO) as a core-forming block, where the dimensional control is poor.
Herein, we demonstrate that the insufficient size control of 2D PPDO
platelets could be overcome through modulation of solvent compositions
or elevating the crystallization temperatures for PPDO. The possible
mechanism involves an improved unimer solubility that avoids fast
unimer aggregation. As a result, uniform 2D platelet micelles with
a controlled area over a substantial size range are created via epitaxial
growth of the unimer. It is noteworthy that the shape control of 2D
platelet micelles from quasi-square to elongated hexagon to lozenge
shapes can be accessible by regulating the crystallization conditions
such as adding different amounts of cosolvents or crystallization
at an elevated temperature. Meanwhile, spatially defined block comicelles
can be achieved via the seeded growth approach from PPDO core-forming
BCPs with different corona functionalities at elevated temperatures.
The excellent water stability and biocompatibility properties of 2D
PPDO platelet micelles further enable them to have a potential application
as cargo vehicles in the drug delivery field.
“…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] …”
In this research paper, we investigated the impact of soft segment crystallization, the cross‐linking density (CLD) and elastic modulus of the synthesized thermoset polyurethanes on their shape memory performance (SMP). A group of tri‐block copolymers of poly(ϵ‐caprolactone) (PCL) and poly(tetramethylene glycol) (PTMG) with PCLx‐PTMG2000‐PCLx architecture were synthesized and used as polyols in a thermoset polyurethane (PU) structure. Crystallization of the soft segments was controlled through changing PCLx blocks’ length. Graphene nanoplatelets, with a fixed content of 0.50 wt.%, was used as the cross‐linker and the nano‐filler to tune elasticity of the PUs. Analysis of crystallization showed that by increasing PCLx’s length from 0 to 2000 D caused a drastic change in the crystallization behavior of the polyols. The polyols used in the thermoset PU nanocomposite led to a wide spectrum of elastic modulus at temperatures close to room temperature. The elastic modulus at room temperature ranged from 20 to 100 MPa. The changes in elastic modulus, CLD and soft segments’ crystallization resulted in a complex SMP behavior, which was studied in‐detail. The shape recovery rate was also studied, which showed the impact of crystallites’ melting, CLD and elastic modulus through a three‐stage shape recovery.
Achieving predictable and programmable two‐dimensional (2D) structures with specific functions from exclusively organic soft materials remains a scientific challenge. This article unravels stereocomplex crystallization‐driven self‐assembly as a facile method for producing thermally robust discrete 2D‐platelets of diamond shape from degradable semicrystalline polylactide (PLA) scaffolds. The method involves co‐assembling two PLA stereoisomers, namely, PY‐PDLA and NMI‐PLLA, which form stereocomplex (SC)‐crystals in isopropanol. By conjugating a well‐known Förster resonance energy transfer (FRET) donor and acceptor dye, namely, pyrene (PY) and naphthalene monoimide (NMI), respectively, to the chain termini of these two interacting stereoisomers, a thermally robust FRET process can be stimulated from the 2D array of the co‐assembled dyes on the thermally resilient SC‐PLA crystal surfaces. Uniquely, by decorating the surface of the SC‐PLA crystals with an externally immobilized guest dye, Rhodamine‐B, similar diamond‐shaped structures could be produced that exhibit pure white‐light emission through a surface‐induced two‐step cascade energy transfer process. The FRET response in these systems displays remarkable dependence on the intrinsic crystalline packing, which could be modulated by the chirality of the co‐assembling PLA chains. This is supported by comparing the properties of similar 2D platelets generated from two homochiral PLLAs (PY‐PLLA and NMI‐PLLA) labeled with the same FRET pair.
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