Electrochemical Manipulation of Aligned Block Copolymer Templates

Petal-like Patterning of Polylactide/Poly (Butylene Succinate) Thin Films Induced by Phase Separation

Biodegradable plastics are attracting attention as a solution to the problems caused by plastic waste. Among biodegradable plastics, polylactide (PLA) and poly (butylene succinate) (PBS) are particularly noteworthy because of their excellent biodegradability. However, the drawbacks of their mechanical properties prompts the need to compound them to achieve the desired strength. The characteristics of the interface of the composite material determine the realization of its final performance. The study of the interface and microstructure of composites is essential for the development of products from degradable polymers. The morphology evolution and microcrystal structure of spin-casted fully biodegradable (PLA/PBS) blend films were investigated using atomic force microscopy (AFM)-based nanomechanical mapping. Results show that intact blend films present an obvious phase separation, where the PBS phase is uniformly dispersed in the PLA phase in the form of pores. Furthermore, the size and number of the PBS phase have a power exponential relationship and linear relationship with PBS loading, respectively. Intriguingly, after annealing at 80 °C for 30 min, the PLA phase formed an orderly petal-like microcrystalline structure centered on the PBS phase. Moreover, the microcrystalline morphology changed from a "daisy type" to a "sunflower type" with the increased size of the PBS phase. Since the size of the PBS phase is controllable, a new method for preparing microscopic patterns using fully biodegradable polymers is proposed.

Multifunctional Structured Platforms: From Patterning of Polymer-Based Films to Their Subsequent Filling with Various Nanomaterials

There is an astonishing number of optoelectronic, photonic, biological, sensing, or storage media devices, just to name a few, that rely on a variety of extraordinary periodic surface relief miniaturized patterns fabricated on polymer-covered rigid or flexible substrates. Even more extraordinary is that these surface relief patterns can be further filled, in a more or less ordered fashion, with various functional nanomaterials and thus can lead to the realization of more complex structured architectures. These architectures can serve as multifunctional platforms for the design and the development of a multitude of novel, better performing nanotechnological applications. In this work, we aim to provide an extensive overview on how multifunctional structured platforms can be fabricated by outlining not only the main polymer patterning methodologies but also by emphasizing various deposition methods that can guide different structures of functional nanomaterials into periodic surface relief patterns. Our aim is to provide the readers with a toolbox of the most suitable patterning and deposition methodologies that could be easily identified and further combined when the fabrication of novel structured platforms exhibiting interesting properties is targeted.

Synthesis and Self-Assembly of Conjugated Block Copolymers

In the past two decades, conjugated polymers (CPs) have drawn great attention due to their excellent conductivity and charge mobility, rendering them broad applications in organic electronics. Controlling over the morphologies and nanostructures of CPs is very important to improve the performance of CP-based devices, which is still a tremendously difficult task. Conjugated block copolymers (cBCPs), composed of different CP blocks or CP coupled with coiled polymeric blocks, not only maintain the advantages of high conductivity and mobility but also demonstrate features of morphological versatility and tunability. Due to the strong π-π interaction and crystallinity of the conjugated backbones, the self-assembly behaviors of cBCPs are very complicated and largely remain to be explored. In this tutorial review, we first summarize the general synthetic methods for different types of cBCPs. Then, recent studies on the self-assembly behaviors of cBCPs are discussed, with an emphasis on the structural factors that affect the morphologies of cBCPs both in bulk and thin film states. Finally, we briefly provide our outlook on the future research of the self-assembly of cBCPs.

Nanoporous Thin Films Formed from Photocleavable Diblock Copolymers on Gold Substrates Modified with Thiolate Self-Assembled Monolayers

Nanoporous thin films formed on electrodes are considered functional elements of electrochemical sensing systems, thus motivating methods for their development. We report a preparative strategy detailing the effects of surface modification of gold substrates with thiolate self-assembled monolayers (SAMs) on the properties of nanoporous thin films derived from polystyrene-block-poly(ethylene oxide) having a photocleavable o-nitrobenzyl ester junction (PS-hν-PEO). Two PS-hν-PEO having similar PEO volume fractions (≈0.2) but different molecular weights (10 and 23 kg/mol) were used to prepare films (30-100 nm thick) spin-cast on gold substrates unmodified and modified with cysteamine, thioctic acid, and 6-hydroxy-1-hexanethiol SAMs. Solvent vapor annealing followed by PEO removal led to the formation of nanopores with average diameters of 12 and 19 nm from the smaller and larger PS-hν-PEO, respectively. Cyclic voltammograms of 1,1'-ferrocenedimethanol showed that nanoporous films on cysteamine SAMs afforded nanopores reaching the underlying substrates at higher density than those on the other substrates. This result was attributed to balanced affinity of the cysteamine SAM surface with PS and PEO, which enhanced the vertical orientation of PEO microdomains. The generation of carboxyl groups associated with the photocleavage reaction was revealed by pH-dependent changes in the voltammogram of Fe(CN)₆^3- that reflected electrostatic effects regulated by the protonation state of the carboxyl groups. The SAMs underneath the nanoporous films could be replaced by treatment with a thiol solution, as verified by voltammograms of l-ascorbic acid. These results suggest that thiolate SAM modification provides a simple means to control the interfacial orientation of PEO microdomains in thin PS-hν-PEO films.