In marine industries, the accumulation of organic matter and marine organisms on ship hulls and instruments limits performance, requiring frequent maintenance and increasing fuel costs. Current coatings technology to combat this biofouling relies heavily on the use of toxic, biocide-containing paints. These pose a serious threat to marine ecosystems, affecting both target and nontarget organisms. Innovation in the design of polymers offers an excellent platform for the development of alternatives, but the creation of a broad-spectrum, nontoxic material still poses quite a hurdle for researchers. Surface chemistry, physical properties, durability, and attachment scheme have been shown to play a vital role in the construction of a successful coating. This review explores why these characteristics are important and how recent research accounts for them in the design and synthesis of new environmentally benign antifouling and fouling release materials.

The benefits of incorporating amphiphilic properties into antifouling and fouling-release coatings are well-established. The use of sequence-defined peptides and peptoids in these coatings allows precise control over the spacing and chemistry of the amphiphilic groups, but amphiphilic peptoids have generally outperformed analogous peptides for reasons attributed to differences in backbone structure. The present work demonstrates that the superior properties of peptoids relative to peptides are primarily attributable to a lack of hydrogen bond donors rather than to their secondary structure. A new amphiphilic peptoid was designed containing functional groups similar to those typically found on a hydrogen-bonding peptide backbone. This peptoid and a non-hydrogen-bonding peptoid analogue were incorporated as side chains in PDMS-based polymer scaffolds. Bioassays with the soft algal fouling organisms Ulva linza and Navicula incerta indicate that hydrogen bonding largely determines the differences seen between similar peptide and peptoid species, while sum frequency generation vibrational spectroscopy suggests that the presence of hydrogen bond donors enhances interfacial water structuring. This reduced initial U. linza adhesion, but attached algae were more strongly bound by hydrogen-bonding interactions. Consequently, amphiphilic peptoid materials lacking hydrogen bond donors are better suited to resist marine fouling, with enhanced release of U. linza and similar performance against N. incerta relative to hydrogen-bonding analogues.

The buildup of organic matter and organisms on surfaces exposed to marine environments, known as biofouling, is a disruptive and costly process affecting maritime operations. Previous research has identified some of the surface characteristics particularly suited to the creation of antifouling and fouling-release surfaces, but there remains room for improvement against both macrofouling and microfouling organisms. Characterization of their adhesives has shown that many rely on oxidative chemistries. In this work, we explore the incorporation of the stable radical 2,2,6,6-tetramethylpipiderin-1-oxyl (TEMPO) as a component in an amphiphilic block copolymer system to act as an inhibitor for marine cements, disrupting adhesion of macrofouling organisms. Using polystyrene-b-poly­(dimethylsiloxane-r-vinylmethysiloxane) block copolymers, pendent vinyl groups were functionalized with TEMPO and poly­(ethylene glycol) to construct an amphiphilic material with redox active character. The antifouling and fouling-release performance of these materials was investigated through settlement and removal assays of three model fouling organisms and correlated to surface structure and chemistry. Surfaces showed significant antifouling character and fouling-release performance was increased substantially toward barnacles by the incorporation of stable radicals, indicating their potential for marine antifouling applications.

A set of controlled surface composition films was produced utilizing amphiphilic block copolymers dispersed in a cross-linked poly(dimethylsiloxane) network. These block copolymers contained oligo(ethylene glycol) (PEGMA) and fluoroalkyl (AF6) side chains in selected ratios and molecular weights to control surface chemistry including antifouling and fouling-release performance. Such properties were assessed by carrying out assays using two algae, the green macroalga Ulva linza (favors attachment to polar surfaces) and the unicellular diatom Navicula incerta (favors attachment to nonpolar surfaces). All films performed well against U. linza and exhibited high removal of attached sporelings (young plants) under an applied shear stress, with the lower molecular weight block copolymers being the best performing in the set. The composition ratios from 50:50 to 60:40 of the AF6/PEGMA side groups were shown to be more effective, with several films exhibiting spontaneous removal of the sporelings. The cells of N. incerta were also removed from several coating compositions. All films were characterized by surface techniques including captive bubble contact angle, atomic force microscopy, and near edge X-ray absorption fine structure spectroscopy to correlate surface chemistry and morphology with biological performance.

Polymers with a triggered decomposition are attractive for an array of applications ranging from patterning to transient packaging materials, as well as for environmental protection. This work showed for the first time UV and thermally triggered transience in fiber mats using poly(propylene carbonate) (PPC) composites. The electrospun PPC-composite fiber mats combine excellent decomposition performance (because of the high surface to volume ratio) with high stiffness and thus represent a new class of materials enabling innovative applications, such as transient filter materials and short-time plant protection materials, as well as temporary lightweight materials for aerospace engineering. Thermally and UV-triggerable additives (protected acids or base) have been used in different concentrations to tune the transience performance of the fiber mats over a wide range (75-212 °C). The addition of organo-modified clay (OMMT) enhanced mechanical stability and prevented shrinkage at room temperature. Different annealing methods have been used to improve the mechanical properties even further (tensile strength = 2-12 MPa, Young's modulus = 55-747 MPa) making these fiber mats attractive for a broad field of applications. An Ashby plot of Young's modulus versus degradation temperature for electrospun fiber mats is shown, revealing much lower degradation temperatures with higher moduli for PPC composites compared to other electrospun polymers.