The increasing prevalence of antibiotic-resistant bacterial infections, coupled with the decline in the number of new antibiotic drug approvals, has created a therapeutic gap that portends an emergent public health crisis. Since the 1980s, host defense peptides (HDPs) have been recognized as antibacterial compounds that do not induce resistance, but are hampered by their high cost and lack of synthetic scalability. Starting in the early 2000s, synthetic (co)polymers have been designed to mimic the salient physiochemical features of HDPs. These polymers have shown broad-spectrum antimicrobial activity, rapid bactericidal kinetics, and a very low propensity to induce resistance. Systematic optimization of the (co)polymer composition, chain length, hydrophobicity, and cationic charge has generated select examples that are also highly biocompatible (non-hemolytic and non-cytotoxic in vitro). These polymers are derived from inexpensive feedstocks and are produced using cost-effective, scalable processes. Accordingly, such polymers may be viewed as early stage pre-clinical candidates for potential use in pharmaceutical or therapeutic applications. In this review, we focus on the key macromolecular design principles that have been gleaned from more than a decade of structure–activity relationship (SAR) studies, as well as some key mechanistic investigations, across this multidisciplinary field. A fundamental understanding of these functional (co)polymers has arisen from a convergence of ideas in polymer chemistry, microbiology, and biophysics. In this context, we emphasize the recent advances from the past few years and emerging opportunities surrounding the rapidly growing field of HDP-mimetic antimicrobial polymers.

Spin and valley degrees of freedom in materials without inversion symmetry promise previously unknown device functionalities, such as spin-valleytronics. Control of material symmetry with electric fields (ferroelectricity), while breaking additional symmetries, including mirror symmetry, could yield phenomena where chirality, spin, valley, and crystal potential are strongly coupled. Here we report the synthesis of a halide perovskite semiconductor that is simultaneously photoferroelectricity switchable and chiral. Spectroscopic and structural analysis, and first-principles calculations, determine the material to be a previously unknown low-dimensional hybrid perovskite (R)-(−)-1-cyclohexylethylammonium/(S)-(+)-1 cyclohexylethylammonium) PbI₃. Optical and electrical measurements characterize its semiconducting, ferroelectric, switchable pyroelectricity and switchable photoferroelectric properties. Temperature dependent structural, dielectric and transport measurements reveal a ferroelectric-paraelectric phase transition. Circular dichroism spectroscopy confirms its chirality. The development of a material with such a combination of these properties will facilitate the exploration of phenomena such as electric field and chiral enantiomer–dependent Rashba-Dresselhaus splitting and circular photogalvanic effects.