Self-Organization-Induced Three-Dimensional Honeycomb Pattern in Structure-Controlled Bulky Methacrylate Polymers:  Synthesis, Morphology, and Mechanism of Pore Formation

Abstract

Here we report, for the first time, a novel molecular design for three-dimensional honeycomb structures through a self-organization of hydrogen-bonded bulky anchoring group in a methacrylic polymer backbone. The polymerizable monomer design includes a methacrylic double bond linked to various hydrophobic anchoring units such as ethane, n-decane, tricyclodecane (TCD), and adamantane via a hydrogen-bonded cycloaliphatic urethane linkage. The structures of the polymers were confirmed by nuclear magnetic resonance (NMR) and the molecular weights of the polymer were determined by gel permeation chromatography (GPC). The methacrylate polymers having tricyclodecane and adamantane bulky anchoring groups self-organized to produce three-dimensional honeycomb patterns in tetrahydrofuran-water solvent mixture at ambient conditions, whereas its linear analogues (ethane, n-decane) failed to produce any micropattern. The scanning electron microscopy (SEM) analysis of the above-prepared polymer films revealed that the structure of the polymer played a major role in the formation of the honeycomb patterns. The solution Fourier transform infrared (FTIR) measurements confirmed that the bulky tricyclodecane and adamantane polymers have strong hydrogen-bonding interaction compared to that of their linear analogues, which is the driving force for the micropatterns. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) analysis of the bulky polymers revealed that the polymers exist as vesicles or micelles in the solution, which leads to the formation of the honeycomb pattern. The honeycomb pattern formation in the bulky polymer systems suggests that two cooperative factors such as hydrogen-bonding interaction and hydrophobicity of bulky anchoring units are necessary to induce three-dimensional honeycomb structures. To investigate the effect of molecular weights and its distribution on the self-organization process, both benzoyl peroxide (BPO) initiated free radical and atom transfer radical polymerization (ATRP) techniques were employed for the polymerization. Micropores formed irrespective of differences in molecular weight and polydispersity index (PDI); however, the pore size distribution was influenced by both molecular weights and PDI. Low molecular weight samples afforded polydisperse pores with the ATRP samples with more narrow PDI producing pores with large dimensions. The approach has also been investigated for polystyrene-bulky methacrylic copolymer, and the results revealed that uniform honeycomb patterns were produced for copolymers having more than 50 mol % incorporation of bulky units.

Breath Figure: A Nature-Inspired Preparation Method for Ordered Porous Films

“…However, most common PIs are insoluble in organic solvents, which limits their use in constructing BFAs. Yabu et al first constructed BFA films with polyion complexes of polyamic acids (74,75) and dialkylammonium salts (76). 287 After a subsequent chemical treatment, polyamic acids were converted to PIs, and dialkylammonium salts were removed from the BFA film.…”

Formation of Films on Water Droplets Floating on a Polymer Solution Surface

“…The “breath figures” method has been broadly applied for obtaining strictly ordered honeycomb patterns with evaporated polymer solutions 1–19. Evaporation of the polymer solution in the humid atmosphere (relative humidity ≈60–80%) brings into existence ordered 2D and 3D structures comprising air holes dispersed in a polymer matrix 1–3,6,9,11.…”

Synthesis of amphiphilic block copolyamines via click reaction

“…Self-assembly of amphiphilic polymers into honey comb structures are influenced by many factors which include the effect of solvents, moisture and polymer concentrations [40]. Based on the reported mechanism of breath figure formation, [21,[41][42][43] it is expected that the polar amine functional groups organize on the surface of the films and are used for the extraction of nanoparticles from aqueous solution. In contrast to this, the polymer solutions in polar, high-boiling solvents such as DMF (0.1 mg mL À1 ) gave spherical particles upon evaporation of solvents under ambient conditions.…”