Synthetic adhesive attachment discs inspired by spider's pyriform silk architecture

Spiders attach their major ampullate silk dragline fibers to surfaces using attachment discs spun from pyriform silk fibers. These attachment discs allow spiders to move safely from place to place while secured to a dragline and to attach their webs to a variety of surfaces. Here, we demonstrate a simple electrospinning process to mimic the “staple‐pin” architecture used by spiders for these attachment discs. Experimental and theoretical evidence are provided to confirm the advantages of thousands of micron‐size “staple‐pins” and their low peeling angles to enhance the adhesive forces required to peel the natural and synthetic attachment discs. These results provide a unique architectural design for fabricating new adhesives that uses very little material for various biomedical and material science applications. © 2014 Wiley Periodicals, Inc. J Polym Sci Part B: Polym. Phys. 2014 , 52, 553–560     

Theoretical perspective on properties of DNA‐functionalized surfaces

The molecular recognition properties of DNA gave rise to many novel materials and applications such as DNA biosensors, DNA‐functionalized colloidal materials, DNA origami and DNA‐based directed surface assembly. The DNA‐functionalized surfaces are used in biosensors and for programmed self‐assembly of biological, organic and inorganic moieties into novel materials. However, surface density, length, and linker design of the surface functionalized DNAs significantly influence the properties of DNA‐driven assemblies and materials. This perspective discusses the understanding of structure and dynamics of DNA immobilized on the surfaces from the theoretical point of view including recent progress in analytical theories, atomistic simulations, and coarse‐grained models. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1563–1568, 2011     

Recent developments in polymeric superoleophobic surfaces

The construction and application of superoleophobic surfaces have aroused worldwide interest during the past few years. These surfaces are of great significance not only for fundamental research but also for various practical applications in self‐cleaning, oil‐repellent coatings, and antibioadhesion. The unique properties of polymers have made them one of the most important materials for constructing superoleophobic materials. This article reviews recent developments in the design, fabrication, and application of polymeric superoleophobic surfaces. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Recent Advances in the Preparation and Applications of Organo‐functionalized Porous Materials

Organo‐functionalized materials with porous structure offer unique adsorption, catalytic and sensing properties. These unique properties make them available for various applications, including catalysis, CO₂ capture and utilization, and drug delivery. The properties and the performance of these unique materials can be altered with suitable modifications on their surface. In this review, we summarize the recent advances in the preparation and applications of organo‐functionalized porous materials with different structures. Initially, a brief historical overview of functionalized porous materials is presented, and the subsequent sections discuss the recent developments and applications of various functional porous materials. In particular, the focus is given on the various methods used for the preparation of organo‐functionalized materials and their important roles in the heterogenization of homogeneous catalysts. A special emphasis is also given on the applications of these functionalized porous materials for catalysis, CO₂ capture and drug delivery.     

A facile synthesis of catechol‐functionalized poly(ethylene oxide) block and random copolymers

Herein we develop a facile synthetic strategy for the functionalization of well‐defined polyether copolymers with control over the number and location of catechol groups. Previously, the functionalization of polyethylene oxide (PEO)‐based polymers with catechols has been limited to functionalization of the chain ends only, hampering the synthesis of adhesive and antifouling materials based on this platform. To address this challenge, we describe an efficient and high‐yielding route to catechol‐functionalized polyethers, which could allow the effects of polymer architecture, molecular weight, and catechol incorporation on the adhesive properties of surface‐anchored PEO to be studied. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2685–2692     

Molecule motion at polymer brush interfaces from single‐molecule experimental perspectives

Polymer brushes have been widely used as functional surface coatings for broad applications including antifouling, energy storage, and lubrications. Understanding the molecule dynamics at polymer brush interfaces is important in unraveling the structure–property relationships in these materials and establishing a new materials design paradigm of novel functional polymer thin films with efficient interfacial transport. By applying modern fluorescence‐based single‐molecule spectroscopic and microscopic techniques, molecule dynamics at varied polymer brush interfaces have been experimentally investigated in recent years. New insights are given to the understandings of some unique and unusual materials properties of polymer brush thin films. This review summarizes some recent studies of molecular diffusion at polymer brush interfaces, highlights some new understandings of the interfacial properties of polymer brushes, and discusses future research opportunities in this field. © 2013 Wiley Periodicals, Inc. J. Polym. Sci. Part B: Polym. Phys. 2014 , 52, 85–103     

Liquid crystal elastomer actuators: Synthesis,alignment, and applications

Liquid crystal elastomers (LCEs) are a unique class of materials which combine rubber elasticity with the orientational order of liquid crystals. This combination can lead to materials with unique properties such as thermal actuation, anisotropic swelling, and soft elasticity. As such, LCEs are a promising class of materials for applications requiring stimulus response. These unique features and the recent developments of the LCE chemistry and processing will be discussed in this review. First, we emphasize several different synthetic pathways in conjunction with the alignment techniques utilized to obtain monodomain LCEs. We then identify the synthesis and alignment techniques used to synthesis LCE‐based composites. Finally, we discuss how these materials are used as actuators and sensors. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 395–411     

Click chemistry in materials synthesis. III. Metal‐adhesive polymers from Cu(I)‐catalyzed azide–alkyne cycloaddition

1,2,3‐Triazole‐based polymers generated from the Cu(I)‐catalyzed cycloaddition between multivalent azides and acetylenes are effective adhesive materials for metal surfaces. The adhesive capacities of candidate mixtures of azide and alkyne components were measured by a modified peel test, using a customized adhesive tester. A particularly effective tetravalent alkyne and trivalent azide combination was identified, giving exceptional strength that matches or exceeds the best commercial formulations. The addition of Cu catalyst was found to be important for the synthesis of stronger adhesive polymers when cured at room temperature. Heating also accelerated curing rates, but the maximum adhesive strengths achieved at both room temperature and high temperature were the same, suggesting that crosslinking reaches the same advanced point in all cases. Polytriazoles also form adhesives to aluminum, but copper is bound more effectively, presumably because active Cu(I) ions may be leached from the surface to promote crosslinking and adhesion. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5182–5189, 2007     

Combinatorial functionalization with bisurea‐peptides and antifouling bisurea additives of a supramolecular elastomeric biomaterial

The bioactive additive toolbox to functionalize supramolecular elastomeric materials expands rapidly. Here we have set an explorative step toward screening of complex combinatorial functionalization with antifouling and three peptide‐containing additives in a bisurea‐based supramolecular system. Thorough investigation of surface properties of thin films with contact angle measurements, X‐ray photoelectron spectroscopy and atomic force microscopy, was correlated to cell‐adhesion of endothelial and smooth muscle cells to apprehend their respective predictive values for functional biomaterial development. Peptides were presented at the surface alone, and in combinatorial functionalization with the oligo(ethylene glycol)‐based non‐cell adhesive additive. The bisurea‐RGD additive was cell‐adhesive in all conditions, whereas the endothelial cell‐specific bisurea‐REDV showed limited bioactive properties in all chemical nano‐environments. Also, aspecific functionality was observed for a bisurea‐SDF1α peptide. These results emphasize that special care should be taken in changing the chemical nano‐environment with peptide functionalization. © 2019 The Authors. Journal of Polymer Science Part B: Polymer Physics published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1725–1735     

The power of thiol‐ene chemistry

As a tribute to Professor Charlie Hoyle, we take the opportunity to review the impact of thiol‐ene chemistry on polymer and materials science over the past 5 years. During this time, a renaissance in thiol‐ene chemistry has occurred with recent progress demonstrating its unique advantages when compared with traditional coupling and functionalization strategies. Additionally, the robust nature of thiol‐ene chemistry allows for the preparation of well‐defined materials with few structural limitations and synthetic requirements. To illustrate these features, the utility of thiol‐ene reactions for network formation, polymer functionalization, dendrimer synthesis, and the decoration of three‐dimensional objects is discussed. Also, the development of the closely related thiol‐yne chemistry is described. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 743–750, 2010     

Integrated surface modification of fully polymeric microfluidic devices using living radical photopolymerization chemistry

Surface modification using living radical polymerization (LRP) chemistry is a powerful technique for surface modification of polymeric substrates. This research demonstrates the ability to use LRP as a polymer substrate surface‐modification platform for covalently grafting polymer chains in a spatially and temporally controlled fashion. Specifically, dithiocarbamate functionalities are introduced onto polymer surfaces using tetraethylthiuram disulfide. This technique enables integration of LRP‐based grafting for the development of an integrated, covalent surface‐modification method for microfluidic device construction. The unique photolithographic method enables construction of devices that are not substrate‐limited. To demonstrate the utility of this approach, both controlled fluid flow and cell patterning applications were demonstrated upon modification with various chemical functionalities. Specifically, poly(ethylene glycol) (375) monoacrylate and trifluoroethyl acrylate were grafted to control fluidic flow on a microfluidic device. Before patterning, surface‐functionalized samples were characterized with both goniometric and infrared spectroscopy to ensure that photografting was occurring through pendant dithiocarbamate functionalities. Near‐infrared results demonstrated conversion of grafted monomers when dithiocarbamate‐functionalized surfaces were used, as compared to dormant control surfaces. Furthermore, attenuated total reflectance/infrared spectroscopy results verified the presence of dithiocarbamate functionalities on the substrate surfaces, which were useful in grafting chains of various functionalities whose contact angles ranged from 7 to 86°. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1404–1413, 2006     

Synthesis and facile end‐group quantification of functionalized PEG azides

Azido‐functionalized poly(ethylene glycol) (PEG) derivatives are finding ever‐increasing applications in the areas of conjugation chemistry and targeted drug delivery by their judicious incorporation into nanoparticle‐forming polymeric systems. Quantification of azide incorporation into such PEG polymers is essential to their effective use. ¹H Nuclear Magnetic Resonance (NMR) analysis offers the simplest approach; however, the relevant adjacent azide‐bearing methylene protons are often obscured by the PEG manifold signals. This study describes the synthesis of 1,2,3‐triazole adducts from their corresponding PEG azides via a convenient, mild click reaction, which facilitates straightforward NMR‐based quantitative end‐group analysis.This method was found to be compatible with many examples of bifunctional azido PEGs with molecular weights ranging from 2 to 18 kDa bearing a variety of functional groups. © 2016 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2888–2895     

Natural underwater adhesives

The general topic of this review is protein‐based underwater adhesives produced by aquatic organisms. The focus is on mechanisms of interfacial adhesion to native surfaces and controlled underwater solidification of natural water‐borne adhesives. Four genera that exemplify the broad range of function, general mechanistic features, and unique adaptations are discussed in detail: blue mussels, acorn barnacles, sandcastle worms, and freshwater caddisfly larva. Aquatic surfaces in nature are charged and in equilibrium with their environment, populated by an electrical double layer of ions as well as adsorbed natural polyelectrolytes and microbial biofilms. Surface adsorption of underwater bioadhesives likely occurs by exchange of surface bound ligands by amino acid sidechains, driven primarily by relative affinities and effective concentrations of polymeric functional groups. Most aquatic organisms exploit modified amino acid sidechains, in particular phosphorylated serines and hydroxylated tyrosines (dopa), with high‐surface affinity that form coordinative surface complexes. After delivery to the surfaces as a fluid, permanent natural adhesives solidify to bear sustained loads. Mussel plaques are assembled in a manner superficially reminiscent of in vitro layer‐by‐layer strategies, with sequentially delivered layers associated through Fe(dopa)₃ coordination bonds. The adhesives of sandcastle worms, caddisfly larva, and barnacles may be delivered in a form somewhat similar to in vitro complex coacervation. Marine adhesives are secreted, or excreted, into seawater that has a significantly higher pH and ionic strength than the internal environment. Empirical evidence suggests these environment triggers could provide minimalistic, fail‐safe timing mechanisms to prevent premature solidification (insolubilization) of the glue within the secretory system, yet allow rapid solidification after secretion. Underwater bioadhesives are further strengthened by secondary covalent curing. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Click chemistry in materials synthesis. 1. Adhesive polymers from copper‐catalyzed azide‐alkyne cycloaddition

The copper(I)‐catalyzed cycloaddition reaction between azides and alkynes has been employed to make metal‐adhesive materials. Copper and brass surfaces supply the necessary catalytic Cu ions, and thus the polymerization process occurs selectively on these metals in the absence of added catalysts. Alternatively, copper compounds can be added to monomer mixtures and then introduced to reducing metal surfaces such as zinc to initiate polymerization. The resulting materials were found to possess comparable or superior adhesive strength to standard commercial glues, and structure‐activity correlations have identified several important properties of the monomers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4392–4403, 2004     

High strength reversible adhesive closures

Closures such as buttons, clasps, zippers, and hook‐and‐loops find widespread use in daily life, and all work by mechanical interlocking. However, these traditional closures are often rigid, lose performance with age, and can produce a harsh sound during use. Here high strength (>50 N cm^?2), reusable, and nearly silent closure devices are fabricated based on recently developed fibril‐less gecko‐inspired adhesives. Guided by a reversible adhesion scaling law, the closure force capacity is tuned by modifying the closure materials and geometry. A simple analytical model is presented which accurately predicts system performance, based on the reversible adhesion scaling parameter. The force capacity of these adhesive closures is measured and compared to commercially‐available hook‐and‐loop closures, and it is found that the adhesive closures sustain forces that are 4.4 times greater for comparable geometry. The sound of release is also quantified and shown to be minimal for adhesive closures. This work provides motivation to develop new high strength, reusable closures for commercial and industrial applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55 , 1783–1790     

Hydration studies in polymer hydrogels

Polymer hydrogels have attracted much interest in recent years based on numerous applications mainly in biotechnology and medicine. For the knowledge‐based design and development of new materials for these and similar applications, it is essential to understand better the hydration properties of hydrogels and of polymers in general. With this term, we mean the particular organization of water in the hydrogel, which determines the properties of the water component, typically different than those of bulk water, and the impact of water on the properties of the polymer matrix itself. In this review, we focus on recent work with hydrogels based on poly(hydroxyethyl acrylate), mostly copolymers with a second hydrophobic polymer and silica nanocomposites. The combination of water sorption/diffusion, thermal and dielectric studies, by fully exploiting the capabilities of each individual technique, proves essential in providing significant information on particular aspects of hydration, such as water uptake, water organization, and diffusion coefficients; glass transition and plasticization; water and polymer dynamics; protonic conductivity, and in revealing interesting correlations between these particular aspects. In the outlook similarities and differences to other related systems, such as protein‐water and polymer solutions in non‐polar solvents, are stressed in the perspective of a broader study. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Properties of acyl modified poly(glycerol‐adipate) comb‐like polymers and their self‐assembly into nanoparticles

There is an increasing need to develop bio‐compatible polymers with an increased range of different physicochemical properties. Poly(glycerol‐adipate) (PGA) is a biocompatible, biodegradable amphiphilic polyester routinely produced from divinyl adipate and unprotected glycerol by an enzymatic route, bearing a hydroxyl group that can be further functionalized. Polymers with an average Mn of ～13 kDa can be synthesized without any post‐polymerization deprotection reactions. Acylated polymers with fatty acid chain length of C₄, C₈, and C₁₈ (PGAB, PGAO, and PGAS, respectively) at different degrees of substitution were prepared. These modifications yield comb‐like polymers that modulate the amphiphilic characteristics of PGA. This novel class of biocompatible polymers has been characterized through various techniques such as FT‐IR, ¹H NMR, surface, thermal analysis, and their ability to self‐assemble into colloidal structures was evaluated by using DLS. The highly tunable properties of PGA reported herein demonstrate a biodegradable polymer platform, ideal for engineering solid dispersions, nanoemulsions, or nanoparticles for healthcare applications. © 2016 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3267–3278     

Peeling of polydimethylsiloxane adhesives: The case of adhesive failure

The adhesion properties of high molecular weight polydimethylsiloxane adhesives are measured using 90°‐peel adhesion tests, in the high velocity range. Such adhesives undergo mainly adhesive failure in this regime. The influence of viscosity (non‐Newtonian), adhesive thickness, peeling velocity, and backing properties are studied, and new unexpected behaviors are shown. The role of rheology and peeling velocity can be explained by an extension of a model already presented for cohesive failure, by using a power‐law fluid for the adhesive. On the other hand, the influence of the backing rigidity reveals to be coupled with the adhesive elastic properties, this effect being correlated to the introduction of a new parameter in the model, the Weissenberg number for viscoelasticity. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2113–2122, 2007     

Preparation of glycopolymer‐coated magnetite nanoparticles for hyperthermia treatment

In this article, magnetite nanoparticles (MNPs) coated with glycopolymer bearing glucose moieties were designed with optimal structural, colloidal, and magnetic properties for biomedical applications. MNPs with an average size of 17 ± 2 nm were synthesized by thermal decomposition process and then their surfaces were modified with active vinyl groups. Two different monomers were immobilized onto the surfaces: dopamine methacrylamide, a monomer with properties inspired on mussels adhesive capacity, or unprotected glycomonomer, 2‐{[(D ‐glucosamin‐2N‐yl)carbonyl]‐oxy}ethyl methacrylate. Afterward, the glycomonomer were polymerized at the interface of both vinyl functionalized MNPs by conventional radical polymerization. The resultant hybrid NPs were water dispersible presenting good stability in aqueous solution for long time periods. Moreover, the high density of carbohydrates at the surface of the magnetic NPs could confer targeting properties to the system as demonstrated by studies of their binding interactions with lectins, where the binding activity is higher as the glycopolymer content augments. The magnetic and magneto‐thermal properties of the synthesized hybrid NPs were evaluated. The magnetization curves reveal superparamagnetic features at 300 K, with high values of saturation magnetization. Furthermore, the hybrid glycoparticles show suitable heat dissipation power when exposed to alternating magnetic field conditions. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

A soft lithography method to generate arrays of microstructures onto hydrogel surfaces

Materials bearing microscale patterns on the surface have important biomedical applications such as scaffolds in tissue engineering, drug delivery systems, sensors, and actuators. Hydrogels are an attractive class of materials that has excellent biocompatibility, biodegradability, and tunable mechanical properties that meet the requirements of the aforementioned applications. Generating patterns of intricate microstructures onto the hydrogel surfaces, however, is challenging due to properties such as the crosslinking density, low mechanical strength, adhesion, or chemical incompatibility of hydrogels with various molds. Here, we report the use of a soft lithography technique to successfully transfer arrays of micropillars onto a poly(2‐hydroxyethyl methacrylate)‐based hydrogel. The swelling of the hydrogel in solvents, such as phosphate‐buffered saline, deionized water, 60% ethanol, and absolute ethanol, facilitates the reproducible replication of the pattern. Furthermore, the micropillar pattern promotes the attachment of HeLa cells onto this hydrogel which is not inherently adhesive when unpatterned. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1144–1157