N-methylol Acrylamide Research Articles

Highly crosslinked polymeric matrix for efficient ultralong dual-mode afterglow with multiple responses

Organic persistent luminescence (OPL) materials have enjoyed a long term research interest for promising applications in optical encryption, bio-imaging and optoelectronic devices. However, to achieve further promotion in afterglow efficiency and stability for responsive OPL systems are still challenging. Herein, an efficient responsive OPL system is prepared by doping an acridine derivative in a highly crosslinked poly(N-methylol acrylamide) matrix. The resulted doped polymeric system exhibits persistent phosphorescence and thermally activated delayed fluorescence with a high afterglow quantum yield up to 82.8% under ambient conditions without photoactivation for oxygen consuming. Benefitted from the dense structure brought by the chemical crosslinking with rich hydrogen bonding, the system exhibits good resistance to different organic solvents and shows response to water without complete afterglow quenching. Moreover, the dual-mode delayed emission consisting of persistent delayed fluorescence and phosphorescence provides time- and temperature-dependent OPL color. Benefitted from the stable feature, high afterglow efficiency and multiple stimuli-responses, the system can serve as OPL inkjet printing, providing potential applications in anti-counterfeiting and data-storage.

Polyhydroxy structure orchestrates the intrinsic antibacterial property of acrylamide hydrogel as a versatile wound-healing dressing.

Hydrogel is considered as a promising candidate for wound dressing due to its tissue-like flexibility, good mechanical properties and biocompatibility. However, traditional hydrogel dressings often fail to fulfill satisfied mechanical, antibacterial, and biocompatibility properties simultaneously, due to the insufficient intrinsic bactericidal efficacy and the addition of external antimicrobial agents. In this paper, hydroxyl-contained acrylamide monomers, N-Methylolacrylamide (NMA) and N-[Tris (hydroxymethyl)methyl] acrylamide (THMA), are employed to prepare a series of polyacrylamide hydrogel dressings xNMA-yTHMA, where x and y represent the mass fractions of NMA and THMA in the hydrogels. We have elucidated that the abundance of hydroxyl groups determines the antibacterial effect of the hydrogels. Particularly, hydrogel 35NMA-5THMA exhibits excellent mechanical properties, with high tensile strength of 259kPa and large tensile strain of 1737%. Furthermore, the hydrogel dressing 35NMA-5THMA demonstrates remarkable inherent antibacterial without exogenous antimicrobial agents owing to the existence of abundant hydroxyl groups. Besides, hydrogel dressing 35NMA-5THMA possesses excellent biocompatibility, in view of marginal cytotoxicity, low hemolysis ratio, and negligible inflammatory response and organ toxicity to mice during treatment. Encouragingly, hydrogel 35NMA-5THMA drastically promote the healing of bacteria-infected wound in mice. This study has revealed the importance of polyhydroxyl in the antibacterial efficiency of hydrogels and provided a simplified strategy to design wound healing dressings with translational potential.

Synthesis and adsorption performance of temperature-sensitive imprinted composite poly (vinylidene fluoride) resin membranes with chitosan modification for selective separation of ReO4−

Purpose This study aims to prepare an imprinted composite membrane with grafted temperature-sensitive blocks for the efficient adsorption and separation of rhenium(Re) from aqueous solutions. Design/methodology/approach PVDF resin membrane was used as the substrate, dopamine and chitosan (CS) were used to modify the membrane surface and temperature-sensitive block PDEA was grafted on the membrane surface. Then acrylic acid (AA) and N-methylol acrylamide (N-MAM) were used as the functional monomers, ethyleneglycol dimethacrylate (EGDMA) as the cross-linker and ascorbic acid-hydrogen peroxide (Vc-H2O2) as the initiator to obtain the temperature-sensitive ReO4− imprinted composite membranes. Findings The effect of the preparation process on the performance of CS–Re–TIICM was investigated in detail, and the optimal preparation conditions were as follows: the molar ratios of AA–NH4ReO4, N-MAM and EGDMA were 0.13, 0.60 and 1.00, respectively. The optimal temperature and time of the reaction were 40 °C and 24 h. The maximum adsorption capacity of CS–Re–TIICM prepared under optimal conditions was 0.1071 mmol/g, and the separation was 3.90 when MnO4− was used as the interfering ion. The quasi first-order kinetics model and Langmuir model were more suitable to describe the adsorption process. Practical implications With the increasing demand for Re, the recovery of Re from Re-containing secondary resources becomes important. This study demonstrated a new material that could be separated and recovered Re in a complex environment, which could effectively alleviate the conflict between the supply and demand of Re. Originality/value This contribution provided a new material for the selective separation and purification of ReO4−, and the adsorption capacity and separation of CS–Re–TIICM were increased with 1.673 times and 1.219 time compared with other Re adsorbents, respectively. In addition, when it was used for the purification of NH4ReO4 crude, the purity was increased from 91.950% to 99.999%.

3D printing a tear-resistant conductive organogel used for wearable sensor

In recent years, ion conductive hydrogels based on photocurable 3D printing technology have attracted wide attention in the application of wearable sensors, which greatly simplifies the manufacturing process of devices, while making devices with high sensitivity and high fidelity. However, the current ionic hydrogel network via photocuring 3D printing is mainly crosslinked by covalent bonds. Due to the lack of sufficient energy dissipation and high-functionality cross-links within the network, the gel will inevitably crack after continuous dynamic loading. Here, we designed an organic gel with excellent tear resistance, which is mainly attributed to the high-functionality cross-links constructed by nano-clay containing a large number of hydroxyl groups. Specifically, the precursor of the organic gel is mainly composed of N-methylol acrylamide (NAM), nano-clays, photoinitiator, and water-glycerol binary solvent system. After photocurable printing, lots of hydrogen bonds are formed between nano-clays and poly-NAM network, which not only provides an energy dissipation mechanism for the gel network, but also acts as a nanoscale cross-linking site to resist crack propagation during the stretching of the gel. Under the action of nano-clay, the tear resistance of the gel has been greatly improved. In addition, the sodium ions released by the nano-clay ensure the good ionic conductivity of the gel, verifying its potential as a strain sensor with high sensitivity. What's more, combining skin-like organic gels and 3D printing technology enables the manufacture of highly sensitive sensors much easier and more designable. This study not only provides a method for the preparation of high-precision ionic conductors with excellent tear resistance, but also clears the way for developing a new class of wearable devices and intelligent electronics.

Fully ceramic microencapsulated fuels with high TRISO particles loading capacity fabricated by gel-casting

A novel gel-casting process for fabrication of the fully ceramic microencapsulated (FCM) fuel with high TRISO particles loading capacity was proposed. In the gel-casting process, silicon carbide (SiC) ceramic was used as matrix, and low toxic N-methylol acrylamide was used as organic monomer with appropriate proportion of cross-linking agent, dispersant, and initiator to achieve the strength of green bodies. FCM fuel pellets with high TRISO particles loading capacity were successfully prepared by SPS process. By using the gel-casting method, the volume fraction of TRISO particles could reach 57%, and the average distance between TRISO particles in a plane was 52.4 μm, which could avoid TRISO particles damage introduced by direct contact between the particles. The structure of SiC matrix was dense and complete, and there was a coherent contact between the matrix and TRISO particles, which ensured the performance and reliability of FCM fuel.

DLP printing of tough organogels for customized wearable sensors

Conductive gels are highly desirable for wearable electronics and sensors. Photocurable 3D printing technology provides an efficient way for the preparation of gel-based microstructured electrodes. However, how to obtain gels with both high stretchability and 3D printability, is still one of the current challenges to customize wearable sensors through 3D printing. Herein, we constructed a photocurable composite mainly composed of N-methylol acrylamide (NAM) and ethylene glycol (EG) for the successful 3D printing of gel-based wearable sensing devices. After printing, abundant hydrogen bonds formed among the hydroxyl groups on the side chains works synergistically with the covalent bonds, enabling the gel to reach excellent mechanical properties and the elongation at break reach 730%. The as-printed gel incorporated with sodium chloride has excellent resistance signal detection ability, which can accurately and stably detect human motion. In addition, the EG endows the printed gels with excellent anti-freezing and anti-drying properties, enabling the wearable sensors to be used in harsh environments. In summary, this work introduced a facile strategy for the rapid preparation of gel-based flexible sensors with microstructure by photocurable 3D printing, which provides the possibilities for the manufacturing of artificial intelligence and smart electronics.

Photo-Curing Chitosan-g-N-Methylolacrylamide Compositions: Synthesis and Characterization

Chitosan is one of the promising compounds for use in various fields of medicine. However, for successful application, materials based on it must be insoluble in water and have specified physical and mechanical properties. In this work, we studied the interaction of N-methylolacrylamide (NMA) and chitosan upon concentration of the solutions, both under the action of UV radiation and without it, which results in curing of the polymer matrix. The main products, proposed mechanisms of the crosslinking reaction, and the influence of external conditions on these processes have been revealed using NMR, IR, and UV spectroscopy. It was found that the reaction proceeds along three pathways. The main reactions proceed with the amino groups of chitosan, and the hydroxymethyl and vinyl groups of NMA. Studies have shown that for the formation of insoluble materials based on chitosan, the best content in the initial cast solution is 2 wt% of chitosan at 0.25 wt% concentration of NMA. Films formed from such solutions possessed high strength and deformation characteristics, namely an elastic modulus of about 1500 GPa, a strength of about 30 MPa, and an elongation at break of about 100%.

In situ polymerization of N-methylol acrylamide (NMA) for bamboo anti-mold modification

Bamboo is an eco-friendly and sustainable material but with limited application due to its susceptibility to mold infection. N-methylol acrylamide (NMA) is a cross-linking monomer with bifunctional groups, here NMA was used to modified bamboo to enhance its anti-mold property through in situ polymerization and cross-linking reaction. When the monomer concentration was 6% and above, no mold germinated at the NMA treated bamboo surface. SEM/EDX, FTIR was used to explore the anti-mold mechanism of NMA modified bamboo. The primary reason for the improvement in the anti-mildew property was the coating effect of PNMA on starch as well as the antimicrobial properties of PNMA. Thermal stability of bamboo before and after modification was almost unchanged. Results also indicated that the mechanical properties of modified bamboo are improved by around 50%, which was mainly attributed to more compact structure of cell wall obtained in the neutral reaction condition. The NMA in situ polymerization was proved to be a potential modification for bamboo to broaden its application.

Influence of Selected Crosslinking Agents and Selected Unsaturated Copolymerizable Photoinitiators Referring to the Shrinkage Resistance of Solvent-Based Acrylic Pressure-Sensitive Adhesives.

The properties of solvent-based pressure-sensitive adhesive (PSA) acrylics, especially shrinkage, are mostly determined by the type and amount of the crosslinking agent added to the prepolymer or by the crosslinking method. The shrinkage profiles of the selected solvent-based acrylic PSA coated on PVC film were investigated using metal chelates (between 0 and 0.55 wt.%), N-methylol acrylamide (up to 8 wt.%), polycarbodiimide and amino resins (up to 6 wt.%), diisocyanate (up to 1 wt.%), multi-functional propylene imines (up to 0.9 wt.%), conventional photoinitiators (up to 3 wt.%) and copolymerizable photoinitiators (up to 2 wt.%). These chemicals were both crosslinking agents that react after the solvent has been evaporated or at higher temperatures, and to the crosslinking agents that react under UV radiation. Some of them were copolymerizable, and others were added to the prepolymer before crosslinking. The best results of shrinkage (0.2%) were obtained by using the UV-crosslinking method and copolymerizable photoinitiators ZLI 3331 and ABP, as well as metal chelates AlACA and TiACA and multifunctional propylene imine Neocryl CX-100 (0.2%). Acceptable results were also achieved for amide BPIA (0.3%), benzophenone derivative PCB (0.4%), N-methylol acrylamide (0.35%) and benzoguanamine resin Cymel 1123 (0.45%).

Competitive reaction effect of vinyl acetate on preparation and characterization of thermosetting starch-based wood adhesives grafted by N-methylol acrylamide

N-methylol acrylamide (NMA) was introduced into a formaldehyde-free starch-based adhesive to improve certain characteristics and achieve a range of important thermosetting properties. The content of NMA in the adhesive was raised to 4% with the addition of 6% vinyl acetate (VAc), in which the wet strength reached 1.4 MPa and the starch accounted for 86.6% of the total solids content. It was observed from thermogravimetric analysis (TGA), Fourier-transform infrared (FTIR) spectroscopy and a residual rate test that VAc could reduce the graft density to avoid gelation, which could be caused by local overgrafting of NMA. In addition, Raman microscopy was applied to prove that uniformity of NMA had been improved by VAc and the preparation of starch-based adhesive with fluidity and better stability was achieved. Chemical shifts in the 1H NMR spectrum and the appearance of a significant shoulder in 13C-CPMAS spectra proved that VAc and NMA were inclined to react via hydroxyl groups at the C6 sites of starch to form a competitive reaction effect in order to inhibit overreaction between NMA and starch. Statistical analysis of the Raman spectra showed that the ingredients of starch reacted with both VAc and NMA, which accounted for 40.3% of the total particles, which played an important role in the water resistance of the resulting adhesives.

Comparative study on cross-linked fluorocarbon acrylate latex

PurposeSelf-crosslinked long fluorocarbon acrylate polymer latex has good hydrophobic and oleophobicity, weather resistance, aging resistance, stability and other excellent properties, which make the polymer be widely used in coatings, dyes, adhesives and other products. The purpose of this study is to prepare self-crosslinked long fluorocarbon acrylate polymer latex via semi-continuous seeded emulsion technology and carry out comparative study on two different cross-linked monomers.Design/methodology/approachMethyl methacrylate (MMA) and butyl acrylate (BA) were used as the main monomers, dodecafluoroheptyl methacrylate (DFMA) as the fluoromonomer, hydroxypropyl methacrylate (HPMA) and N-methylol acrylamide (NMA) as cross-linked monomers, and 1-allyloxy-3–(4-nonylphenol)-2-propanol polyoxyethylene (10) ether (ANPEO10) and 1-allyloxy-3–(4-nonylphenol)-2-propanol polyoxyethylene (10) ether ammonium sulfate (DNS-86) as compound emulsifiers via the semicontinuous-seeded emulsion polymerization.FindingsThe properties of the polymer emulsions, which are prepared with two different cross-linked monomers, are compared and discussed, and it is concluded that HPMA is more suitable for the preparation of self-crosslinked polymer emulsions. The formula of the polymer latex is ANPEO10: DNS-86 = 1:1, and the mass ratio of the monomers used in the polymer is MMA: BA: DFMA: HPMA = 14.40:14.40:0.60:0.60.Practical implicationsSelf-crosslinked long fluorocarbon acrylate polymer latex can be used in many fields such as coatings, dyes, adhesives and other products.Originality/valueThe self-crosslinked long fluorocarbon acrylate polymer latex is prepared by mixing the nonionic emulsifier ANPEO10 and the anionic emulsifier DNS-86 when potassium persulfate is used as the thermal decomposition initiator and the semicontinuous-seeded emulsion technology is adopted and the comparative study on two different cross-linked monomer is carried out, which is not reported in the open literatures.

Reducible, recyclable and reusable (3R) hydrogel electrolyte membrane based on Physical&Chemical Bi-networks and reversible sol-gel transition

Hydrogel electrolytes are attracting growing interest in the various fields, and tremendous efforts have been widely made for enhancing the hydrogel electrolyte of flexible devices. However, conventional hydrogel electrolytes generally contain non-degradable and non-renewable polymer matrix materials, inevitably causing waste of resources and environmental pollution, which fundamentally restricts the utilization of hydrogel electrolyte in the aspect of energy storage device during daily use. In this work, a novel flexible hydrogel electrolyte, that can be reducible, recyclable, and reusable (3R), is fabricated through physical and chemistry double crosslinking among carboxylated chitosan, N-methylol acrylamide, N, N′-methylene bisacrylamide, and potassium persulfate, followed by intense uptake of Li2SO4 electrolyte. The hydrogel electrolyte membrane displays high ionic conductivity of 3.52 × 10−2 S cm−1, and exhibits 348.92% electrolyte uptake., The flexible quasi-solid supercapacitor assembled with the hydrogel electrolyte shows remarkable electrochemical performance like high capacitance retention of 83% and outstanding energy density of 8.74 Wh kg−1. Interestingly, the renewable performance of hydrogel electrolyte membrane is observed when the hydrogel electrolyte membrane suffered from heating to cooling cycle, which allows to easily realize multiple regeneration of electrolyte membrane based on the reversible sol-gel transition. This work provides a promising route to design a hydrogel electrolyte membrane with infinite regeneration times for flexible energy storage devices in the future.

TiO2 Nanoparticle-Loaded Poly(NIPA-co-NMA) Fiber Web for the Adsorption and Photocatalytic Degradation of 4-Isopropylphenol.

A TiO2 nanoparticle-loaded polymer fiber web was developed as a functional material with the ability to adsorb and photo-catalytically degrade organic pollutants in aquatic media. A linear copolymer of N-isopropylacrylamide (primary component) and N-methylol acrylamide (poly(NIPA-co-NMA)) was prepared, and composite fibers were fabricated by electrospinning a methanol suspension containing the copolymer and commercially available TiO2 nanoparticles. The crosslinking of the polymer via the formation of methylene bridges between NMA units was accomplished by heating, and the fiber morphology was analyzed by electron microscopy. 4-Isopropylphenol generated by the degradation of bisphenol A—one of the endocrine-disrupting chemicals—was used as the model organic pollutant. As poly(NIPA) is a thermosensitive polymer that undergoes hydrophilic/hydrophobic transition in water, the temperature-dependence of the adsorption and photocatalytic degradation of 4-isopropylphenol was investigated. The degradation rate was analyzed using a pseudo-first-order kinetic model to obtain the apparent reaction rate constant, kapp. The enhancement of the photocatalytic degradation rate owing to the adsorption of 4-isopropylphenol onto thermosensitive poly(NIPA)-based fibers is discussed in terms of the ratio of the kapp of the composite fiber to that of unsupported TiO2 nanoparticles. Based on the results, an eco-friendly wastewater treatment process involving periodically alternated adsorption and photocatalytic degradation is proposed.

Importance of Dynamic Mechanical Analysis to Predict Performance of the Polyvinyl Acetate Wood Adhesives in Summer Season

Conventionally available Polyvinyl acetate (PVAc) wood glues are polyvinyl alcohol (PVA) stabilized, with drawbacks like poor strength at high humidity, poor strength at high temperature and workability at low-temperature. PVAc is non-resistant to high humidity, and if such adhesive bonds are exploited in a highly humid environment, its strength substantially decreases. Sufficiently water-resistant adhesive bonds are achieved by modifying PVAc dispersion with special chemicals like acrylic acid (AA) and N-methylol acrylamide (NMA) as a co-monomer, Silanes, and ethylene modified PVA. The Lewis acids like aluminium chloride and aluminium nitrate are used as cross-linkers. So PVAc adhesives are classified as reactive and non-reactive glue. Application of non-reactive D1 (as per EN 204-205) and reactive D2 and D3 (as per EN 204-205) adhesives for bonding laminate on plywood is a regular practice in the Indian market. In summer time, Crack formation was seen in laminate bonded with reactive D2 and D3 adhesives in regions where the room temperature was above 45°C. However, if the same laminate substrates were bonded with non-reactive D1, no cracks were seen. To analyse the above phenomenon, we have done Dynamic mechanical analysis of non-reactive D1, reactive D2 and D3 adhesive.

Transparent, Conductive Hydrogels with High Mechanical Strength and Toughness.

Transparent, conductive hydrogels with good mechanical strength and toughness are in great demand of the fields of biomedical and future wearable smart electronics. We reported a carboxymethyl chitosan (CMCS)–calcium chloride (CaCl2)/polyacrylamide (PAAm)/poly(N-methylol acrylamide (PNMA) transparent, tough and conductive hydrogel containing a bi-physical crosslinking network through in situ free radical polymerization. It showed excellent light transmittance (>90%), excellent toughness (10.72 MJ/m3), good tensile strength (at break, 2.65 MPa), breaking strain (707%), and high elastic modulus (0.30 MPa). The strain sensing performance is found with high sensitivity (maximum gauge factor 9.18, 0.5% detection limit), wide strain response range, fast response and recovery time, nearly zero hysteresis and good repeatability. This study extends the transparent, tough, conductive hydrogels to provide body-surface wearable devices that can accurately and repeatedly monitor the movement of body joints, including the movements of wrists, elbows and knee joints. This study provided a broad development potential for tough, transparent and conductive hydrogels as body-surface intelligent health monitoring systems and implantable soft electronics.

Poly (acrylic acid-co-N-methylol acrylamide-co-butyl acrylate) copolymer grafted carboxymethyl cellulose binder for silicon anode in lithium ion batteries

A poly (acrylic acid-co-N-methylol acrylamide-co-butyl acrylate) copolymer grafted-carboxymethyl cellulose (PA-PN-PBA-g-CMC) binder is synthesized via a free radical copolymerization for Si-based anodes in lithium ion batteries. In this multifunctional polymer binder system, carboxyl-rich poly (acrylic acid) and carboxymethyl cellulose can bond with Si particles and copper current collectors. Additionally, a robust cross-linking network can be obtained through the condensation reaction between hydroxyl and hydroxymethyl groups which are present in carboxymethyl cellulose and N-methylol acrylamide segments, respectively. This network structure helps to keep the integrity of the Si electrode, and thereby significantly improves the cycling performance of the Si anodes (capacity retention rate after 200 cycles is above 90%). The butyl groups in poly (butyl acrylate) segments provide the nonpolar sections in the binder, which help the electrolytes easily wet the electrodes, allowing Li ions to diffuse rapidly in the Si anodes. With this multi-functional binder, the Si-based LIBs perform well in both cycle performance and rate performance.

On-line enrichment and determination of aristolochic acid in medicinal plants using a MOF-based composite monolith as adsorbent

In this study, modified UiO-66-NH2 and N-methylolacrylamide (NMA) were used as common monomers to prepare a metal organic framework (MOF)-based composite monolith through in-situ polymerization, which was used as a new adsorbent to purify and enrich aristolochic acid-I (AA-I) in medicinal plants. The MOF-based composite monolithic column was characterized by nitrogen adsorption–desorption isotherm, mercury intrusion porosimetry and scanning electron microscopy (SEM). The adsorption ability of MOF-based composite monolith for AA-I was compared with that of the polymer monolith without MOF added. The results proved that the addition of UiO-66-NH2 can increase both the specific surface area and the permeability of the monolith. Moreover, the adsorption amount of AA-I on the monolith improved. This proposed on-line solid phase extraction (SPE) method showed good linear relationship in the range 0.044 ~ 400 μg/mL with r = 0.9994; the limit of detection (LOD) was 13.08 ng/mL and the limit of quantification (LOQ) was 44.00 ng/mL; the intra-day and inter-day accuracies were less than 0.97%; the inter-column accuracies was less than 6.11%; the recovery was in the range of 91.11%~106.48%. The method was found to be easy, accurate and convenient for on-line enrichment and purification of AA-I in medicinal plants.

Temperature-responsive iron nanozymes based on poly(N-vinylcaprolactam) with multi-enzyme activity.

Iron (Fe)-based nanozymes are widely applied in the biomedical field due to their enzyme-like catalytic activity. Herein, Fe(ii)-based coordination polymer nanohydrogels (FeCPNGs) have been conveniently prepared as a new type of nanozyme by the chelation reaction between ferrous iron and polymer nanohydrogels. The P(VCL-co-NMAM) nanohydrogels prepared by a reflux precipitation polymerization method using N-vinylcaprolactam (VCL) and N-methylol acrylamide (NMAM) as monomers and N,N-methylenebisacrylamide (MBA) as a crosslinker were esterified using P2O5 and then chelated with Fe(ii) ions to form nanozymes with peroxidase and superoxide dismutase (SOD) activity. It was found by dynamic light scattering (DLS) and transmission electron microscopy (TEM) that the nanohydrogels prepared with a monomer concentration of 4% and mass ratio of 1 : 1 (VCL : NMAM) had more uniform particle size, better dispersion and a distinct temperature response. The results of Fourier transform infrared (FTIR), DLS, TEM, X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) indicated the successful preparation of the esterified nanohydrogel and FeCPNGs. Of particular importance is that such FeCPNGs can functionally mimic two antioxidant enzymes (peroxidase and superoxide dismutase) by UV analysis of catalytic oxidation between 3,3,5,5-tetramethylbenzidine (TMB) and H2O2 and the kit analysis of SOD-like activity.

Preparation of novel chitosan derivatives and applications in functional finishing of textiles

A novel chitosan derivative, O-acrylamidomethyl-N-[(2-hydroxy-3- dimethyldodecylammonium) propyl] chitosan chloride (NMA-HDCC), was synthesized by reacting chitosan (CTS) with epoxypropyl dodecyl dimethyl quaternary ammonium salt and N-methylolacryl amide (NMA). The chemical structure of the quaternized chitosan was analyzed by FTIR and NMR. The water soluble derivative can form covalent bonding with cellulosic fibers and bring quaternary salt groups onto the fibers. Anti-bacterial as well as salt-free reactive dyeing properties of the treated cotton samples were analyzed. The NMA-HDCC treated cotton fabrics showed durable antimicrobial functions even after 30 consecutive home launderings. The cotton treated with the chitosan and different chitosan derivatives showed improved uptakes, fixation rates, K/S values and fastness of reactive dyes without using auxiliary salt.

Eye-recognizable and repeatable biochemical flexible sensors using low angle-dependent photonic colloidal crystal hydrogel microbeads

This paper presents eye-recognizable and repeatable biochemical flexible sensors using low angle-dependent stimuli-responsive photonic colloidal crystal hydrogel (PCCG) microbeads. Thanks to the stimuli-responsive PCCG microbeads exhibiting structural color, users can obtain sensing information without depending on the viewing angle and the mechanical deformation of the flexible sensor. Temperature-responsive PCCG microbeads and ethanol-responsive PCCG microbeads were fabricated from a pre-gel solution of N-isopropylacrylamide (NIPAM) and N-methylolacrylamide (NMAM) by using a centrifuge-based droplet shooting device (CDSD). As a proof-of-concept of thin and flexible biochemical sensors, temperature- and ethanol-sensing devices were demonstrated. By comparing the structural color of the stimuli-responsive PCCG microbeads and the color chart of the device, sensing information, including skin temperature of the human body and ethanol concentration in alcoholic beverages, was obtained successively. We expect that our device design using low angle-dependent stimuli-responsive PCCG microbeads would contribute to the development of user-friendly biochemical sensor devices for monitoring environmental and healthcare targets.