Abstract
Herein, we report the formation and characterization of novel amphiphilic linear-dendritic block copolymers (LDBCs) composed of hydrophilic dendritic poly(ether-ester), PEE, blocks and hydrophobic linear poly(styrene), PSt. The LDBCs are synthesized via controlled atom transfer radical polymerization (ATRP) initiated by a PEE macroinitiator. The copolymers formed have narrow molecular mass distributions and are designated as LGn-PSt Mn, in which LG represents the PEE fragment, n denotes the generation of the dendron (n = 1–3), and Mn refers to the average molecular mass of the LDBC (Mn = 3.5–68 kDa). The obtained LDBCs are utilized to fabricate honeycomb films by a static “breath figure” (BF) technique. The copolymer composition strongly affects the film morphology. LDBCs bearing acetonide dendron end groups produce honeycomb films when the PEE fraction is lower than 20%. Pore uniformity increases as the PEE content decreases. For LDBCs with hydroxyl end groups, only the first generation LDBCs yield BF films, but with a significantly smaller pore size (0.23 μm vs. 1–2 μm, respectively). Although higher generation LDBCs with free hydroxyl end groups fail to generate honeycomb films by themselves, the use of a cosolvent or addition of homo PSt leads to BF films with a controllable pore size (3.7–0.42 μm), depending on the LDBC content. Palladium complexes within the two triazole groups in each of the dendron’s branching moieties can also fine-tune the morphology of the BF films.
Highlights
Polymer films with well-ordered micro- or nanosized pores are attractive to researchers due to their potential applications including, but not limited to, filters [1,2,3], sensors [4,5,6], cell culture media [7], photoelectronic devices [8,9], and templating materials [10]
The water droplets grow in size, arrange into hexagonally packed arrays stabilized by a polymer precipitate, and eventually sink deeper into the polymer solution, subsequently serving as templates for ordered pores [12,13]
The initial attempt to prepare PEE-block-PSt linear-dendritic block copolymers (LDBCs) was conducted by the coupling strategy (a) using PEE
Summary
Polymer films with well-ordered micro- or nanosized pores are attractive to researchers due to their potential applications including, but not limited to, filters [1,2,3], sensors [4,5,6], cell culture media [7], photoelectronic devices [8,9], and templating materials [10]. The surface of the polymer solution cools down as the solvent evaporates and promotes the condensation of water onto it. The water droplets grow in size, arrange into hexagonally packed arrays stabilized by a polymer precipitate, and eventually sink deeper into the polymer solution, subsequently serving as templates for ordered pores [12,13]. Since the introduction of the BF technique in 1994 by Francois [14], Polymers 2019, 11, 539; doi:10.3390/polym11030539 www.mdpi.com/journal/polymers
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