Probing the Analogy between Living Crystallization-Driven Self-Assembly and Living Covalent Polymerizations: Length-Independent Growth Behavior for 1D Block Copolymer Nanofibers
英文:
Probing the Analogy between Living Crystallization-Driven Self-Assembly and Living Covalent Polymerizations: Length-Independent Growth Behavior for 1D Block Copolymer Nanofibers
著者
和文:
Shixing Lei,
Jia Tian,
福井智也,
Mitchell A. Winnik,
Ian Manners.
英文:
Shixing Lei,
Jia Tian,
Tomoya Fukui,
Mitchell A. Winnik,
Ian Manners.
Living crystallization-driven self-assembly (CDSA) is of growing interest as a seeded growth route to colloidally stable one-dimensional (1D) and two-dimensional (2D) nanoparticles and more complex hierarchical assemblies with low size dispersity and predetermined dimensions from crystallizable polymeric and molecular amphiphiles. The origin of the low size dispersities has previously been explained in terms of an analogy between living CDSA with living covalent polymerizations of molecular monomers, in particular, for the case where initiation is faster than propagation and chain terminating or chain breaking processes are absent. Recently, based on Brownian dynamics simulations, an alternative explanation for this behavior involving length-dependent growth has been suggested for 1D fiber-like micelle formation where the growth rate decreases as the length increases. Herein, we have investigated this possibility experimentally by comparing the simultaneous growth from relatively short (Ln = ca. 100 nm) and long (Ln = ca. 1000 nm) seed fibers derived from crystallizable poly(ferrocenyldimethylsilane) (PFS) block copolymers with polar or nonpolar corona-forming blocks. Using a statistical analysis of fiber lengths based on transmission electron microscopy (TEM) data, we found that the growth rate from the termini of the short and long fibers was identical within experimental error in either polar or nonpolar media at both ambient (22 °C) and elevated (35 °C) temperatures. Analogous length-independent growth was found for the case of the formation of fiber-like triblock comicelles and for 1D micelles with a different, crystallizable poly(fluorenetrimethylenecarbonate) (PFTMC) core-forming block. The results therefore strongly indicate that the low dispersities characteristic of living CDSA processes do not arise from a gradual reduction in growth rate with fiber length. The length-independent growth observed experimentally is therefore consistent with the previously proposed explanation for length control and low dispersities based on an analogy with living covalent polymerizations of molecular monomers.
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