Multitemperature Memory Actuation of a Liquid Crystal Polymer Network over a Broad Nematic–Isotropic Phase Transition Induced by Large Strain

The shape change of a polymer actuator based on liquid crystal network (LCN) generally occurs over a relatively sharp LC-isotropic phase transition. Reported herein is the discovery of an unusual phenomenon and the enabled actuation control for LCN. The smectic phase of a LCN with mesogenic moieties on the chain backbone can be suppressed by high elongation of the specimen, which gives rise to a broad nematic–isotropic phase transition. Consequently, the actuation force and related shape of the actuator can be activated to a given degree by easily varying the temperature over a wide range (35 K for LCN prepared with 500% strain) to adjust the proportion of the order–disorder phase transition. This reversible multitemperature memory actuation can translate into many stable and interconvertible shapes with one single LCN actuator

Multitemperature Memory Actuation of a Liquid Crystal Polymer Network over a Broad Nematic–Isotropic Phase Transition Induced by Large Strain

The shape change of a polymer actuator based on liquid crystal network (LCN) generally occurs over a relatively sharp LC-isotropic phase transition. Reported herein is the discovery of an unusual phenomenon and the enabled actuation control for LCN. The smectic phase of a LCN with mesogenic moieties on the chain backbone can be suppressed by high elongation of the specimen, which gives rise to a broad nematic–isotropic phase transition. Consequently, the actuation force and related shape of the actuator can be activated to a given degree by easily varying the temperature over a wide range (35 K for LCN prepared with 500% strain) to adjust the proportion of the order–disorder phase transition. This reversible multitemperature memory actuation can translate into many stable and interconvertible shapes with one single LCN actuator

Multitemperature Memory Actuation of a Liquid Crystal Polymer Network over a Broad Nematic–Isotropic Phase Transition Induced by Large Strain

The shape change of a polymer actuator based on liquid crystal network (LCN) generally occurs over a relatively sharp LC-isotropic phase transition. Reported herein is the discovery of an unusual phenomenon and the enabled actuation control for LCN. The smectic phase of a LCN with mesogenic moieties on the chain backbone can be suppressed by high elongation of the specimen, which gives rise to a broad nematic–isotropic phase transition. Consequently, the actuation force and related shape of the actuator can be activated to a given degree by easily varying the temperature over a wide range (35 K for LCN prepared with 500% strain) to adjust the proportion of the order–disorder phase transition. This reversible multitemperature memory actuation can translate into many stable and interconvertible shapes with one single LCN actuator

Multitemperature Memory Actuation of a Liquid Crystal Polymer Network over a Broad Nematic–Isotropic Phase Transition Induced by Large Strain

The shape change of a polymer actuator based on liquid crystal network (LCN) generally occurs over a relatively sharp LC-isotropic phase transition. Reported herein is the discovery of an unusual phenomenon and the enabled actuation control for LCN. The smectic phase of a LCN with mesogenic moieties on the chain backbone can be suppressed by high elongation of the specimen, which gives rise to a broad nematic–isotropic phase transition. Consequently, the actuation force and related shape of the actuator can be activated to a given degree by easily varying the temperature over a wide range (35 K for LCN prepared with 500% strain) to adjust the proportion of the order–disorder phase transition. This reversible multitemperature memory actuation can translate into many stable and interconvertible shapes with one single LCN actuator

Multitemperature Memory Actuation of a Liquid Crystal Polymer Network over a Broad Nematic–Isotropic Phase Transition Induced by Large Strain

The shape change of a polymer actuator based on liquid crystal network (LCN) generally occurs over a relatively sharp LC-isotropic phase transition. Reported herein is the discovery of an unusual phenomenon and the enabled actuation control for LCN. The smectic phase of a LCN with mesogenic moieties on the chain backbone can be suppressed by high elongation of the specimen, which gives rise to a broad nematic–isotropic phase transition. Consequently, the actuation force and related shape of the actuator can be activated to a given degree by easily varying the temperature over a wide range (35 K for LCN prepared with 500% strain) to adjust the proportion of the order–disorder phase transition. This reversible multitemperature memory actuation can translate into many stable and interconvertible shapes with one single LCN actuator

Ultrathin Antifouling Coatings with Stable Surface Zwitterionic Functionality by Initiated Chemical Vapor Deposition (iCVD)

Antifouling thin films of poly­[<i>N</i>,<i>N</i>-dimethyl-<i>N</i>-methacryloxyethyl-<i>N</i>-(3-sulfopropyl)-<i>co</i>-2-(dimethylamino)­ethyl methacrylate<i>-co</i>-ethylene glycol dimethacrylate] (PDDE) were synthesized via a substrate-independent and all-dry-initiated chemical vapor deposition (iCVD) technique followed by a diffusion-limited vapor-phase reaction with 1,3-propane sultone. Coated surfaces exhibited very low absorption of various foulants including bovine serum albumin (BSA), humic acid (HA), and sodium alginate (SA), as measured with the quartz crystal microbalance with dissipation monitoring (QCM-D). The fouling by humic acid was dependent on the presence of divalent cations such as Ca²⁺. Both depth profiling and angle-resolved X-ray photoelectron spectroscopy (XPS) measurements indicated that the zwitterionic groups were highly concentrated in the top ∼3 nm of the film. The contact angle measurements revealed a limited degree of surface chain reorganization upon contacting water. The dynamic contact angles remained unchanged after 100 days of storage in air, indicating the stability of the interface. The coating was substrate-independent, and the film was conformal on surface nanostructures including trenches, reverse osmosis membranes, and electrospun nanofiber mats

Amphiphilic Copolymer Thin Films with Short Fluoroalkyl Side Chains for Antibiofilm Properties at the Solid–Liquid–Air Interface

Biofouling is a critical problem that limits numerous technologies including water desalination and marine transportation. The existing solutions, such as copper-based paint to mitigate ship hull fouling, are known to harm aquatic species. Although hydrophilic and zwitterionic materials have demonstrated great promise in resisting the formation of biofilms, they demonstrated limited effectiveness at the solid–liquid–air interface, the location most prone to biofilm formation by motile bacteria. While an amphiphilic copolymer comprising a statistical mixture of zwitterionic and fluorinated units exhibited excellent antifouling performance at the triple interface, the long-fluorinated side chain raises concerns regarding bioaccumulation. Here, two amphiphilic copolymers, each made of a pyridinium-based zwitterionic and hydrophobic repeat units with a short fluorinated chain (1H,1H,2H,2H-perflurooctyl and 2,2,3,4,4,4-hexafluorobutyl groups), were synthesized using initiated chemical vapor deposition. Fineman–Ross analysis demonstrated the formation of random copolymers with a preference for 4-vinylpyridine incorporation. The antibiofilm performance remained good for both hydrophobic chains: amphiphilic copolymers outperformed pure zwitterionic chemistry by 43.8 and 39.3%, as demonstrated usingPseudomonas aeruginosathat forms biofilms at the triple interface. The amphiphilic coatings reported here can be used to prevent biofilm formation at the triple interface in marine transportation, food manufacturing, and medical devices, while avoiding the environmental concerns related to perfluoroalkyl substances

Zwitterionic Antifouling Coatings for the Purification of High-Salinity Shale Gas Produced Water

Fouling refers to the undesirable attachment of organic molecules and microorganisms to submerged surfaces. It is an obstacle to the purification of shale gas produced water and is currently without an effective solution due to the highly contaminated nature of produced water. Here, we demonstrate the direct vapor application of a robust zwitterionic coating to a variety of substrates. The coating remains unprecedentedly hydrophilic, smooth, and effectively antifouling in extremely high salinity solutions (with salt concentration of 200 000 ppm). The fouling resistance is assessed rapidly and quantitatively with a molecular force spectroscopy-based method and corroborated using quartz crystal microbalance system with dissipation monitoring. Grazing angle attenuated total reflectance Fourier transform infrared is used in combination with X-ray photoelectron spectroscopy, atomic force microscope, and <i>in situ</i> spectroscopic ellipsometry to lend insight into the underlying mechanism for the exceptional stability and effectiveness of the zwitterionic coating under high-salinity conditions. A unique coating architecture, where the surface is concentrated with mobile zwitterionic moieties while the bulk is cross-linked to enhance coating durability, was discovered to be the origin of its stable fouling resistance under high salinity. Combined with previously reported exceptional stability in highly oxidative environments and strong fouling resistance to oil and grease, the zwitterionic surface here has the potential to enable low-cost, membrane-based techniques for the purification of produced water and to eventually balance the favorable economics and the concerning environmental impacts of the hydraulic fracturing industry

Controllable Cross-Linking of Vapor-Deposited Polymer Thin Films and Impact on Material Properties

We report the single-step preparation of controllably cross-linked poly­(divinylbenzene) (PDVB) and poly­(4-vinylpyridine-<i>co</i>-divinylbenzene) thin films using initiated chemical vapor deposition (iCVD). Fourier transform infrared spectroscopy-based methods for quantifying film composition and degree of cross-linking are elucidated; the validity of these methods is assessed using X-ray photoelectron spectroscopy and nanoindentation. The extent of reaction of divinylbenzene (DVB) pendant vinyl bonds in homo- and copolymer films is unaffected by changes in initiator concentration, suggesting that bond reactivity, rather than radical concentration, is the limiting factor. Analysis of film step coverage (<i>S</i>) over high aspect ratio (AR) features and sticking probability calculations lend insight into the reactivity of both monomers and explain the extreme conformality of PDVB films (<i>S</i> = 0.87 ± 0.02 at AR = 4.7). In addition, the incorporation and cross-linking of DVB moieties in the copolymer are extremely reproducible and can be used to tune the elastic moduli of the films from 3.4 to 5.8 GPa

Molecular fouling resistance of zwitterionic and amphiphilic initiated chemically vapor-deposited (iCVD) thin films

<div><p>Biofouling is a universal problem in various applications ranging from water purification to implantable biomedical devices. Recent advances in surface modification have created a rich library of antifouling surface chemistries, many of which can be categorized into one of the two groups: hydrophilic surfaces or amphiphilic surfaces. We report the straightforward preparation of antifouling thin film coatings in both categories via initiated chemical vapor deposition. A molecular force spectroscopy-based method is demonstrated as a rapid and quantitative assessment tool for comparing the differences in antifouling characteristics. The fouling propensity of single molecules, as opposed to bulk protein solution or bacterial culture, is assessed. This method allows for the interrogation of molecular interaction without the complication resulted from protein conformational change or micro-organism group interactions. The molecular interaction follows the same trend as bacterial adhesion results obtained previously, demonstrating that molecular force probe is a valid method for the quantification and mechanistic examination of fouling. In addition, the molecular force spectroscopy-based method is able to distinguish differences in antifouling capability that is not resolvable by traditional static protein adsorption tests. To lend further insight into the intrinsic fouling resistance of zwitterionic and amphiphilic surface chemistries, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, advancing and receding water contact angles, and atomic force microscopy are used to elucidate the film properties that are relevant to their antifouling capabilities.</p></div