Spatially Restricted Templated Growth of Poly(ε-caprolactone) from Carbon Nanotubes by Crystallization-Driven Self-Assembly

Abstract

The fabrication of hybrid hierarchical assemblies involving inorganic and organic building blocks has received a significant amount of attention as a result of their facile tunability and potential applications. However, precise design of hybrid hierarchical architectures still remains a challenge because of the difficulty of precise control over design and the incompatibility of organic and inorganic building blocks. Crystallization-driven self-assembly (CDSA) of block copolymers is a powerful method in the preparation of complex semicrystallized structures from the nano- to microscale, with controlled shape and uniform size. Herein, we extended the scope of this methodology in the construction of hybrid micellar CDSA brushes on functionalized carbon nanotubes (CNTs). Tunable brushlike heterostructures containing both CNTs and CDSA nanoassemblies were fabricated by anchoring the short crystalline seeds of PCL-b-P4VP [PCL = poly­(ε-caprolactone) and P4VP = poly­(4-vinylpyridine)] onto CNTs through the hydrogen bond and by a further in situ CDSA process via the addition of PCL-b-PDMA [PDMA = poly­(N,N-dimethylacrylamide)] unimers. More importantly, the shapes of PCL-b-PDMA crystals changed from two-dimensional platelets to long and thin crystals with increasing mass ratios of seed micelles to CNTs. Moreover, further exploration indicated that only one end of the immobilized seeds could initiate the growth of PCL-b-PDMA crystals, while the other end failed to enable growth because of the spatial confinement of CNTs.

Lateral growth of cylinders

“…The T g of PAzoMA was 63.1 °C, while the melting point was 100.4 °C. The melting enthalpy (Δ H m ) of PAzoMA was measured to be 6.62 J g ‒1 , which is much lower than that of reported typical crystalline and azobenzene-containing polymers 35 , 36 . Assuming that a purely crystalline sample has a typical value of Δ H m ≈ 150−300 J g −1, 37 the crystallinity of PAzoMA is estimated to be ~ 4−8%.…”

An Amphiphilic Corona-Forming Block Promotes Formation of a Variety of 2D Platelets via Crystallization-Driven Block Copolymer Self-Assembly

“…The earliest examples of CDSA, with polyethylene glycol (PEG) as the core-forming block, led to square platelet structures. − Later examples, with poly­(ferrocenyldimethylsilane) (PFS) as the core-forming block and shorter corona-forming chains generated more ribbon-like planar (2D) structures, with the core characterized as a single crystal. , Core-crystalline 2D micelles formed by CDSA have now been reported for block copolymers with a broad variety of different core-forming blocks. Examples include polyethylene (PE), , poly­(3-hexylthiophene) (P3HT), , polycaprolactone (PCL), − and poly­( L -lactide) (PLLA). , In most cases, when the corona/core block ratios were less than 2, the BCPs tended to form 2D platelets. − There are a few exceptions where BCPs with long corona chains prefer to form elongated 2D structures. , Up to now, several types of 2D platelet structures have been fabricated, including squares, ,, rectangles, ,,− diamonds, ,, ellipsoidal or lenticular ovals, ,,− and hexagonal disks. , However, the factors that control the size and shape of these platelets and how they vary with sample preparation protocols are poorly understood.…”

Patchy Micelles with a Crystalline Core: Self-Assembly Concepts, Properties, and Applications

“…Next to BCPs with a PFS block, a variety of other crystallizable polymer blocks were employed in CDSA, e.g. polyethylene (PE) [ 68 , 92 , 93 , 94 ], poly(ethylene oxide) [ 95 ], polyesters (poly( ε -caprolactone) (PCL) or poly( L -lactide) (PLLA)) [ 86 , 96 , 97 , 98 , 99 , 100 , 101 ], polycarbonate [ 102 ], poly(2- iso -propyl-2-oxazoline) (P i PrOx) [ 103 , 104 ], liquid crystalline polymers [ 71 , 105 ], poly(vinylidene fluoride) [ 106 ], polypeptoids [ 107 , 108 ], and various conjugated polymers (e.g., poly(3-hexyl thiophene) (P3HT) and OPV) [ 75 , 109 , 110 , 111 , 112 , 113 ].…”