Synthesis and characterization of photoactive poly(arylene ether sulfone)s containing azobenzene moieties in their main chains

Compatible Photochromic Systems for Opto-electronic Applications

Today, a lot of attention is paid to remote controlled opto-electronic devices. Many of them are commonly used in the society, industry, and science. Accessories dedicated to the particular utilization are desired. The point is to find a simple way to obtain smart and functional appliances. Materials engineering faces such problems and provides a variety of solutions concerning advanced material design, preparation, and utilization. Photochromic materials represent one of the already known materials, which still find other objectives in new fields of life. In our work, we present two differently constructed photoresponsive polymers, which give significantly different nonlinear optical (NLO) response visible as noticeable optical signal modulation. By playing with diversified laser light energy or its frequency, NLO output characterized appealing, and individual characteristics (doubled Δn ∼0.02 vs 0.04 and entirely different kinetics for two similar materials and the same laser pumping). Interestingly, high output signal repeatability and stability were achieved, which indicate the investigated materials as promising candidates in the construction of various opto-electronic devices. Additionally, a set of photoresponsive studies, reflectometry, and theoretical insights was performed and included in this work.

Design of Collective Motions from Synthetic Molecular Switches, Rotors, and Motors

Precise control over molecular movement is of fundamental and practical importance in physics, biology, and chemistry. At nanoscale, the peculiar functioning principles and the synthesis of individual molecular actuators and machines has been the subject of intense investigations and debates over the past 60 years. In this review, we focus on the design of collective motions that are achieved by integrating, in space and time, several or many of these individual mechanical units together. In particular, we provide an in-depth look at the intermolecular couplings used to physically connect a number of artificial mechanically active molecular units such as photochromic molecular switches, nanomachines based on mechanical bonds, molecular rotors, and light-powered rotary motors. We highlight the various functioning principles that can lead to their collective motion at various length scales. We also emphasize how their synchronized, or desynchronized, mechanical behavior can lead to emerging functional properties and to their implementation into new active devices and materials.

Resistive memory devices based on novel functionalized poly(aryl ether)s with pendant azobenzene

We designed and synthesized two novel azobenzene functionalized poly(aryl ether)s (PAEs), PAE-azo-1 and PAE-azo-2, from a new azobenzene monomer via nucleophilic aromatic substitution polycondensation. This direct polymerization approach via azobenzene monomer has the advantages of controlling the distribution and amount of the azobenzene chromophores in the polymer. Both of the polymers showed very good thermal stability and excellent solubility for future application in the electronics industry. These polymers were fabricated as films by simple spin-coating and both of them were then prepared as sandwich memory devices. PAE-azo-1 and PAE-azo-2 exhibit write-once-read-many-times-type memory behavior, which can be encoded as “0” and “1,” and possess the low operation voltage below −3.0 V. The memory mechanism was investigated through ultraviolet–visible optical absorption spectrum and the cyclic voltammetry. These obtained results indicate that the novel azobenzene functionalized PAEs are a promising candidate for low power consumption and high-performance materials for data storage.

Long-term stability at high temperatures for birefringence in PAZO/PAH layer-by-layer films

Optical memories with long-term stability at high temperatures have long been pursued in azopolymers with photoinduced birefringence. In this study, we show that the residual birefringence in layer-by-layer (LbL) films made with poly[1-[4-(3-carboxy-4 hydroxyphenylazo)benzene sulfonamido]-1,2-ethanediyl, sodium salt] (PAZO) alternated with poly(allylamine hydrochloride) (PAH) can be tuned by varying the extent of electrostatic interactions with film fabrication at different pHs for PAH. The dynamics of both writing and relaxation processes could be explained with a two-stage mechanism involving the orientation of the chromophores per se and the chain movement. Upon calculating the activation energies for these processes, we demonstrate semiquantitatively that reduced electrostatic interactions in films prepared at higher pH, for which PAH is less charged, are responsible for the longer stability at high temperatures. This is attributed to orientation of PAZO chromophores via cooperative aggregation, where the presence of counterions hindered relaxation.