Micromolding of Thermoplastic Polymers for Direct Fabrication of Discrete, Multilayered Microparticles

Soft lithography provides a convenient and effective method for the fabrication of microdevices with uniform size and shape. However, formation of an embossed, connective film as opposed to discrete features has been an enduring shortcoming associated with soft lithography. Removing this residual layer requires additional postprocessing steps that are often incompatible with organic materials. This limits adaptation and widespread realization of soft lithography for broader applications particularly in drug discovery and drug delivery fields. A novel and versatile approach is demonstrated that enables fabrication of discrete, multilayered, fillable, and harvestable microparticles directly from any thermoplastic polymer, even at very high molecular weights. The approach, isolated microparticle replication via surface-segregating polymer blend mold, utilizes a random copolymer additive, designed with a highly fluorinated segment that, when blended with the mold's matrix, spontaneously orients to the surface conferring an extremely low surface energy and nonwetting properties to the template. The extremely nonwetting properties of the mold are further utilized to load soluble biologics directly into the built-in microwells in a rapid and efficient manner using an innovative screen-printing approach. It is believed that this approach holds promise for fabrication of large-array, 3D, complex microstructures, and is a significant step toward clinical translation of microfabrication technologies.

Investigating the effect of grafting density on the surface properties for sequence-determined fluoropolymer films

Six sequence-determined fluoropolymers were synthesized and their surface properties were affected by their grafting densities. The reason can be attributed to the assembled structure of the perfluoroalkyl chains at the surface.

Surface Segregation of Amphiphilic PDMS-Based Films Containing Terpolymers with Siloxane, Fluorinated and Ethoxylated Side Chains

(Meth)acrylic terpolymers carrying siloxane (Si), fluoroalkyl (F) and ethoxylated (EG) side chains were synthesized with comparable molar compositions and different lengths of the Si and EG side chains, while the length of the fluorinated side chain was kept constant. Such terpolymers were used as surface-active modifiers of polydimethylsiloxane (PDMS)-based films with a loading of 4 wt%. The surface chemical compositions of both the films and the pristine terpolymers were determined by angle-resolved X-ray photoelectron spectroscopy (AR-XPS) at different photoemission angles. The terpolymer was effectively segregated to the polymer−air interface of the films independent of the length of the constituent side chains. However, the specific details of the film surface modification depended upon the chemical structure of the terpolymer itself. The exceptionally high enrichment in F chains at the surface caused the accumulation of EG chains at the surface as well. The response of the films to the water environment was also proven to strictly depend on the type of terpolymer contained. While terpolymers with shorter EG chains appeared not to be affected by immersion in water for seven days, those containing longer EG chains underwent a massive surface reconstruction.

Dynamic surface antifouling: mechanism and systems

Marine biofouling is a global problem today. High efficiency and eco-friendly antifouling systems are in pressing need. In recent years, we have proposed the concept of dynamic surface antifouling (DSA). That is, a continuously changing surface can effectively prevent marine fouling organisms from landing and adhesion. Based on this strategy, we developed coatings with dynamic surfaces by using degradable polymers including polyester-polyurethane, modified polyester and poly(ester-co-acrylate). They exhibit tunable renewability, and excellent antifouling and mechanical performance. Moreover, the polymers can serve as carrier and controlled release systems of antifoulants so that they have long service life. This paper reviews the progress and trends in marine anti-biofouling, and presents the mechanism and systems of DSA.

Recent advances in organic–inorganic well-defined hybrid polymers using controlled living radical polymerization techniques

Controlled living radical polymerizations, such as ATRP and RAFT polymerization, could be utilized for the preparation of well-defined organic–inorganic hybrid polymers based on POSS, PDMS, silica nanoparticles, graphene, CNTs and fullerene.

Effects of surface-active block copolymers with oxyethylene and fluoroalkyl side chains on the antifouling performance of silicone-based films

Block copolymers made from a poly(dimethyl siloxane) (Si) and a poly(meth)acrylate carrying oxyethylene (EG) or fluoroalkyl (AF) side chains were synthesized and incorporated as surface-active components into a silicone matrix to produce cross-linked films with different surface hydrophilicity/phobicity. Near-edge X-ray absorption fine structure (NEXAFS) studies showed that film surfaces containing Si-EG were largely populated by the siloxane, with the oxyethylene chains present only to a minor extent. In contrast, the fluorinated block was selectively segregated to the polymer-air interface in films containing Si-AF as probed by NEXAFS and X-ray photoelectron spectroscopy (XPS) analyses. Such differences in surface composition were reflected in the biological performance of the coatings. While the films with Si-EG showed a higher removal of both Ulva linza sporelings and Balanus amphitrite juveniles than the silicone control, those with Si-AF exhibited excellent antifouling properties, preventing the settlement of cyprids of B. amphitrite.

Semi fluorinated polymers as surface energy controlled layers for liquid crystal alignment

The effects of compounded hydrogenated–fluorinated surfaces formed by perfluorocyclobutane (PFCB)-containing polymers on the alignment of a liquid crystal, 4,4′-octylcycanobiphenyl (8CB), were investigated.

Copolymer films containing amphiphilic side chains of well-defined fluoroalkyl-segment length with biofouling-release potential

Novel methacrylate copolymers containing polysiloxane (SiMA) and mixed poly(ethyleneglycol)-perfluorohexyl side chains (MEF) were synthesised and dispersed as surface-active additives in crosslinked PDMS films.

Microphase Structure, Crystallization Behavior, and Wettability Properties of Novel Fluorinated Copolymers Poly(perfluoroalkyl acrylate-co-stearyl acrylate) Containing Short Perfluorohexyl Chains

Novel fluorinated copolymers of stearyl acrylate (SA) and (perfluorohexyl)ethyl acrylate (C6A), (perfluorohexyl)ethyl methacrylate (C6MA), 2-[[[[2-(perfluorohexyl)]-sulfonyl]methyl] amino]ethyl acrylate (C6SA), and methacrylate (C6SMA) were synthesized via miniemulsion copolymerization. The extremely hydrophobic monomers perfluoroalkyl acrylate (FA) and SA acted as the reactive costabilizer in the miniemulsion system. The microstructure and surface wetting properties of the copolymers were characterized by (1)H NMR, FT-IR, and dynamic contact angle test. The crystallization behaviors and fine surface structures of the copolymer films were determined by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) analysis. The self-assembled aggregation and roughness of the copolymer films were investigated by atomic force microscopy (AFM). The results showed that the fluorinated side chains interrupted and impeded the crystallizable side chains of SA from forming complete crystals. And the Tm and ΔHf of the copolymers were decreased as a consequence of this effect. The fluorinated side chains in P(C6A/SA) and P(C6MA/SA) arranged between the crystallizable hydrocarbon side chains of SA, while the crystallization structure of fluorinated and nonfluorinated pendant groups existed all at once in copolymers P(C6SA/SA) and P(C6SMA/SA). The four copolymers exhibited very low surface free energy and excellent dynamic water repellency attributed to the restriction of perfluoroalkyl groups combined with crystallization of stearyl pendant groups.

A comparison between different fouling-release elastomer coatings containing surface-active polymers

Surface-active polymers derived from styrene monomers containing siloxane (S), fluoroalkyl (F) and/or ethoxylated (E) side chains were blended with an elastomer matrix, either poly(dimethyl siloxane) (PDMS) or poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS), and spray-coated on top of PDMS or SEBS preformed films. By contact angle and X-ray photoelectron spectroscopy measurements, it was found that the surface-active polymer preferentially populated the outermost layers of the coating, despite its low content in the blend. However, the self-segregation process and the response to the external environment strongly depended on both the chemistry of the polymer and the type of matrix used for the blend. Additionally, mechanical testing showed that the elastic modulus of SEBS-based coatings was one order of magnitude higher than that of the corresponding PDMS-based coatings. The coatings were subjected to laboratory bioassays with the marine alga Ulva linza. PDMS-based coatings had superior fouling-release properties compared to the SEBS-based coatings.

An ecotoxicological study on tin- and bismuth-catalysed PDMS based coatings containing a surface-active polymer

Novel films were prepared by condensation curing reaction of a poly(dimethyl siloxane) (PDMS) matrix with bismuth neodecanoate and dibutyltin diacetate catalysts. An ecotoxicological study was performed on the leachates of the coatings using the bacterium Vibrio fischeri, the unicellular alga Dunaliella tertiolecta, the crustacean Artemia salina and the fish Sparus aurata (larvae) as testing organisms. A copper-based self-polishing commercial paint was also tested as reference. The results showed that the tin-catalysed coatings and the copper paint were highly toxic against at least two of the four test organisms, whereas bismuth-catalysed coatings did not show any toxic effect. Moreover, the same biological assessment was also carried out on PDMS coatings containing a surface-active fluorinated polymer. The toxicity of the entire polymeric system resulted only from the tin catalyst used for the condensation curing reaction, as the bismuth catalysed coatings incorporating the surface-active polymer remained atoxic toward all the tested organisms.

Interfacial characteristics of a PEGylated imidazolium bistriflamide ionic liquid electrolyte at a lithium ion battery cathode of LiMn2O4

Nonvolatile and nonflammable ionic liquids (ILs) have distinct thermal advantages over the traditional organic solvent electrolytes of lithium ion batteries. However, this beneficial feature of ILs is often counterbalanced by their high viscosity (a limiting factor for ionic conductivity) and, sometimes, by their unsuitable electrochemistry for generating protective layers on electrode surfaces. In an effort to alleviate these limiting aspects of ILs, we have synthesized a PEGylated imidazolium bis(trifluoromethylsulfonyl)amide (bistriflamide) IL that exhibited better thermal and electrochemical stability than a conventional electrolyte based on a blend of ethylene carbonate and diethyl carbonate. The electrochemical performance of this IL has been demonstrated using a cathode consisting of ball-milled LiMn2O4 particles. A direct comparison of the ionic liquid electrolyte with the nonionic low-viscosity conventional solvent blend is presented.