Orthogonal surface functionalization through bioactive vapor-based polymer coatings

Systematic Studies into the Area Selectivity of Chemical Vapor Deposition Polymerization

As the current top-down microchip manufacturing processes approach their resolution limits, there is a need for alternative patterning technologies that offer high feature densities and edge fidelity with single-digit nanometer resolution. To address this challenge, bottom-up processes have been considered, but they typically require sophisticated masking and alignment schemes and/or face materials' compatibility issues. In this work, we report a systematic study into the impact of thermodynamic processes on the area selectivity of chemical vapor deposition (CVD) polymerization of functional [2.2]paracyclophanes (PCP). Adhesion mapping of preclosure CVD films by atomic force microscopy (AFM) provided a detailed understanding of the geometric features of the polymer islands that form under different deposition conditions. Our results suggest a correlation between interfacial transport processes, including adsorption, diffusion, and desorption, and thermodynamic control parameters, such as substrate temperature and working pressure. This work culminates in a kinetic model that predictes both area-selective and nonselective CVD parameters for the same polymer/substrate ensemble (PPX-C + Cu). While limited to a focused subset of CVD polymers and substrates, this work provides an improved mechanistic understanding of area-selective CVD polymerization and highlights the potential for thermodynamic control in tuning area selectivity.

Design Strategies for Structurally Controlled Polymer Surfaces via Cyclophane-Based CVD Polymerization and Post-CVD Fabrication

Molecular structuring of soft matter with precise arrangements over multiple hierarchical levels, especially on polymer surfaces, and enabling their post-synthetic modulation has tremendous potential for application in molecular engineering and interfacial science. Here, recent research and developments in design strategies for structurally controlled polymer surfaces via cyclophane-based chemical vapor deposition (CVD) polymerization with precise control over chemical functionalities and post-CVD fabrication via orthogonal surface functionalization that facilitates the formation of designable biointerfaces are summarized. Particular discussion about innovative approaches for the templated synthesis of shape-controlled CVD polymers, ranging from 1D to 3D architecture, including inside confined nanochannels, nanofibers/nanowires synthesis into an anisotropic media such as liquid crystals, and CVD polymer nanohelices via hierarchical chirality transfer across multiple length scales is provided. Aiming at multifunctional polymer surfaces via CVD copolymerization of multiple precursors, the structural and functional design of the fundamental [2.2]paracyclophane (PCP) precursor molecules, that is, functional CVD monomer chemistry is also described. Technologically advanced and innovative surface deposition techniques toward topological micro- and nanostructuring, including microcontact printing, photopatterning, photomask, and lithographic techniques such as dip-pen nanolithography, showcasing research from the authors' laboratories as well as other's relevant important findings in this evolving field are highlighted that have introduced new programmable CVD polymerization capabilities. Perspectives, current limitations, and future considerations are provided.

Improved hemocompatibility of polysulfone hemodialyzers with Endexo® surface modifying molecules

Anticoagulation therapy is widely used to reduce clotting during hemodialysis (HD), but may cause adverse effects in end-stage kidney disease patients. A new hemodialyzer with a membrane modified by surface modifying molecule was developed to improve hemocompatibility that aimed to reduce the need for anticoagulation during dialysis treatments. We compared membrane surface characteristics and in vitro hemocompatibility of the new hemodialyzer to the standard polysulfone (PSF) hemodialyzer membrane. Scanning electron microscopy, contact angle measurement (68° ± 3° test vs. 41.6° ± 6° control), and X-ray photoelectron spectrometry measurement for fluorine atomic % (7.4% ± 0.4% test vs. not detectable control), showed that the membrane surface was modified with surface modifying macromolecule (SMM1) but maintained membrane structure and surface hydrophilicity. Zeta potential of the blood-contacting surface showed that the absolute surface charge was reduced at neutral pH (-3.3 mV ± 1.1 mV test vs. -15.6 mV ± 1.0 mV control). Platelet count reduction was significantly less for the SMM1-modified dialyzer (40.88% ± 21.89%) compared to the standard PSF dialyzer (62.62% ± 34.13%), along with Platelet Factor 4 (1824.10 ng/ml ± 436.26 ng/ml test vs. 2479.00 ng/ml ± 852.96 ng/ml control). These studies demonstrate the successful incorporation of SMM1 into the new hemodialyzer with the expected results. Our in vitro experiments indicate that the SMM1-modified hemodialyzers could improve hemocompatibility compared to standard PSF hemodialyzers and have the potential to minimize the patient's anticoagulant requirements during HD. Additional research with SMM1 additives incorporated into the entire dialysis circuit and use in a clinical settings are required to confirm these promising findings.

Chemically Tunable Organic Dielectric Layer on an Oxide TFT: Poly(p-xylylene) Derivatives

Inorganic materials such as SiO_x and SiN_x are commonly used as dielectric layers in thin-film transistors (TFTs), but recent advancements in TFT devices, such as inclusion in flexible electronics, require the development of novel types of dielectric layers. In this study, CVD-deposited poly(p-xylylene) (PPx)-based polymers were evaluated as alternative dielectric layers. CVD-deposited PPx can produce thin, conformal, and pinhole-free polymer layers on various surfaces, including oxides and metals, without interfacial defects. Three types of commercial polymers were successfully deposited on various substrates and exhibited stable dielectric properties under frequency and voltage sweeps. Additionally, TFTs with PPx as a dielectric material and an oxide semiconductor exhibited excellent device performance; a mobility as high as 22.72 cm²/(V s), which is the highest value among organic gate dielectric TFTs, to the best of our knowledge. Because of the low-temperature deposition process and its unprecedented mechanical flexibility, TFTs with CVD-deposited PPx were successfully fabricated on a flexible plastic substrate, exhibiting excellent durability over 10000 bending cycles. Finally, a custom-synthesized functionalized PPx was introduced into top-gated TFTs, demonstrating the possibility for expanding this concept to a wide range of chemistries with tunable gate dielectric layers.

Tooth-Supporting Hard Tissue Regeneration Using Biopolymeric Material Fabrication Strategies

The mineralized tissues (alveolar bone and cementum) are the major components of periodontal tissues and play a critical role to anchor periodontal ligament (PDL) to tooth-root surfaces. The integrated multiple tissues could generate biological or physiological responses to transmitted biomechanical forces by mastication or occlusion. However, due to periodontitis or traumatic injuries, affect destruction or progressive damage of periodontal hard tissues including PDL could be affected and consequently lead to tooth loss. Conventional tissue engineering approaches have been developed to regenerate or repair periodontium but, engineered periodontal tissue formation is still challenging because there are still limitations to control spatial compartmentalization for individual tissues and provide optimal 3D constructs for tooth-supporting tissue regeneration and maturation. Here, we present the recently developed strategies to induce osteogenesis and cementogenesis by the fabrication of 3D architectures or the chemical modifications of biopolymeric materials. These techniques in tooth-supporting hard tissue engineering are highly promising to promote the periodontal regeneration and advance the interfacial tissue formation for tissue integrations of PDL fibrous connective tissue bundles (alveolar bone-to-PDL or PDL-to-cementum) for functioning restorations of the periodontal complex.

Recent Advances in Recoverable Systems for the Copper-Catalyzed Azide-Alkyne Cycloaddition Reaction (CuAAC)

The explosively-growing applications of the Cu-catalyzed Huisgen 1,3-dipolar cycloaddition reaction between organic azides and alkynes (CuAAC) have stimulated an impressive number of reports, in the last years, focusing on recoverable variants of the homogeneous or quasi-homogeneous catalysts. Recent advances in the field are reviewed, with particular emphasis on systems immobilized onto polymeric organic or inorganic supports.

Selective and Reversible Binding of Thiol-Functionalized Biomolecules on Polymers Prepared via Chemical Vapor Deposition Polymerization

We use chemical vapor deposition polymerization to prepare a novel dibromomaleimide-functionalized polymer for selective and reversible binding of thiol-containing biomolecules on a broad range of substrates. We report the synthesis and CVD polymerization of 4-(3,4-dibromomaleimide)[2.2]paracyclophane to yield nanometer thick polymer coatings. Fourier transformed infrared spectroscopy and X-ray photoelectron spectroscopy confirmed the chemical composition of the polymer coating. The reactivity of the polymer coating toward thiol-functionalized molecules was confirmed using fluorescent ligands. As a proof of concept, the binding and subsequent release of cysteine-modified peptides from the polymer coating were also demonstrated via sum frequency generation spectroscopy. This reactive polymer coating provides a flexible surface modification approach to selectively and reversibly bind biomolecules on a broad range of materials, which could open up new opportunities in many biomedical sensing and diagnostic applications where specific binding and release of target analytes are desired.