Zeolitic imidazolate framework (ZIF) membranes are emerging as a promising energy-efficient separation technology. However, their reliable and scalable manufacturing remains a challenge. We demonstrate the fabrication of ZIF nanocomposite membranes by means of an all-vapor-phase processing method based on atomic layer deposition (ALD) of ZnO in a porous support followed by ligand-vapor treatment. After ALD, the obtained nanocomposite exhibits low flux and is not selective, whereas after ligand-vapor (2-methylimidazole) treatment, it is partially transformed to ZIF and shows stable performance with high mixture separation factor for propylene over propane (an energy-intensive high-volume separation) and high propylene flux. Membrane synthesis through ligand-induced permselectivation of a nonselective and impermeable deposit is shown to be simple and highly reproducible and holds promise for scalability.

Vapor-deposited polymer thin films empower the next-generation biological applications including bio-separations, biosensors & bio-MEMS, drug delivery and tissue engineering.

An imidazolium-based zwitterionic polymer is reported with dual functions of antivirus and antifouling with broad applicability.

Conformal coating of ultrahigh-aspect-ratio nanostructures with functional polymer thin films is highly desirable in many applications, ranging from biosensing to energy storage. Nevertheless, achieving uniform surface coverage on nanostructures is challenging due to the difficulty of controlling molecular transport and reaction kinetics under nanoconfinement. Here we demonstrated the conformal coverage of ultrahigh-aspect-ratio nanopores by polymer nanolayers deposited using initiated chemical vapor deposition (iCVD) and unraveled the fundamental mechanisms governing the coating growth kinetics under nanoconfinement. A molecular-collision model was developed by using statistical methods and validated by systematic kinetic experiments. The results indicated that nanoconfinement amplified radical− surface collisions, resulting in higher effective radical concentration. The approach for validating the molecular-collision model can be broadly adopted to study vapor-based reaction systems without needing extensive nanofabrication or characterization instruments. Together, the results reported here could improve the control over nanocoating growth during nanostructured material/device fabrications across industries of manufacturing, healthcare, and sustainability.

Initiated Chemical Vapor Deposition (iCVD) is a free-radical polymerization technique used to synthesize functional polymer thin films. In the context of drug delivery, the conformality of iCVD coatings and the variety of functional chemical moieties make them excellent materials for encapsulating pharmaceutics. Poly(4-aminostyrene) (PAS) belongs to a class of functionalizable materials, whose primary amine allows decoration of the delivery vehicles with biomolecules that enable targeted delivery or biocompatibility. Understanding kinetics of PAS polymerization in iCVD is crucial for such deployments because drug release kinetics in thin-film encapsulation have been shown to be determined by the film thickness. Nevertheless, the effects of deposition conditions on PAS growth kinetics have not been studied systematically. To bridge that knowledge gap, we report the kinetics of iCVD polymerization as a function of fractional saturation pressure of the monomer (i.e., Pm/Psat) in a dual-regime fashion, with quadratic dependence under low Pm/Psat and linear dependence under high Pm/Psat. We uncovered the critical Pm/Psat value of 0.2, around which the transition also occurs for many other iCVD monomers. Because existing theoretical models for the iCVD process cannot fully explain the dual-regime polymerization kinetics, we drew inspiration from solution-phase polymerization and proposed updated termination mechanisms that account for the transition between two regimes. The reported model builds upon existing iCVD theories and allows the synthesis of PAS thin films with precisely controlled growth rates, which has the potential to accelerate the deployment of iCVD PAS as a novel biomaterial in controlled and targeted drug delivery with designed pharmacokinetics.

Due to the emergence of wide-spread infectious diseases, there is a heightened need for antimicrobial and/or antifouling coatings that can be used to prevent infection and transmission in a variety...

Conformal coating of nanopores with functional polymer nanolayers is the key to many emerging technologies such as miniature sensors and membranes for advanced molecular separations. While the polymer coatings are often used to introduce functional moieties, their controlled growth under nanoconfinement could serve as a new approach to manipulate the size and shape of coated nanopores, hence, enabling novel functions like molecular separation. However, precise control of coating thickness in the longitudinal direction of a nanopore is limited by the lack of a characterization method to profile coating thickness within the nanoconfined space. Here, we report an experimental approach that combines ion milling (IM) and high-resolution field emission scanning electron microscopy (FESEM) for acquiring an accurate depth profile of ultrathin (∼20 nm or less) coatings synthesized inside nanopores via initiated chemical vapor deposition (iCVD). The enhanced capability of this approach stems from the excellent x–y resolution achieved by FESEM (i.e., 4.9 nm/pixel), robust depth ( z) control enabled by IM (step size as small as 100 nm with R2 = 0.992), and the statistical power afforded by high-throughput sampling (i.e., ∼2000 individual pores). With that capability, we were able to determine with unparalleled accuracy and precision the depth profile of coating thickness and iCVD kinetics along 110-nm-diameter nanopores. That allowed us to uncover an unexpected coating depth profile featuring a maximum rate of polymerization at ∼250 nm underneath the top surface, i.e., down the pores, which we termed “necking.” The necking phenomenon deviates considerably from the conventionally assumed monotonous decrease in thickness along the longitudinal direction into a nanopore, as predicted by the diffusion-limited kinetics model of free radical polymerization. An initiator-centric collision model was then developed, which suggests that under the experimental conditions, the confinement imposed by the nanopores may lead to local amplification of the effective free radical concentration at z ≤ 100 nm and attenuation at z ≥ 500 nm, thus contributing to the observed necking phenomenon. The ion-milling-enabled depth profiling of ultrathin coatings inside nanopores, along with the initiator-mediated coating thickness control in the z-direction, may serve to enhance the performance of size-exclusion filtration membranes and even provide more flexible control of nanopore shape in the z dimension.

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.