Aminopropyl-terminated Polydimethylsiloxane Research Articles

AgNP Composite Silicone-Based Polymer Self-Healing Antifouling Coatings.

Biofouling poses a significant challenge to the marine industry, and silicone anti-biofouling coatings have garnered extensive attention owing to their environmental friendliness and low surface energy. However, their widespread application is hindered by their low substrate adhesion and weak static antifouling capabilities. In this study, a novel silicone polymer polydimethylsiloxane (PDMS)-based poly(urea-thiourea-imine) (PDMS-PUTI) was synthesized via stepwise reactions of aminopropyl-terminated polydimethylsiloxane (APT-PDMS) with isophorone diisocyanate (IPDI), isophthalaldehyde (IPAL), and carbon disulfide (CS2). Subsequently, a nanocomposite coating (AgNPs-x/PDMS-PUTI) was prepared by adding silver nanoparticles (AgNPs) to the polymer PDMS-PUTI. The dynamic multiple hydrogen bonds formed between urea and thiourea linkages, along with dynamic imine bonds in the polymer network, endowed the coating with outstanding self-healing properties, enabling complete scratch healing within 10 min at room temperature. Moreover, uniformly dispersed AgNPs not only reduced the surface energy of the coating but also significantly enhanced its antifouling performance. The antibacterial efficiency against common marine bacteria Pseudomonas aeruginosa (P.sp) and Staphylococcus aureus (S.sp) was reduced by 97.08% and 96.71%, respectively, whilst the diatom settlement density on the coating surface was as low as approximately 59 ± 3 diatom cells/mm2. This study presents a novel approach to developing high-performance silicone antifouling coatings.

Innovative Synthesis of Photo-Responsive, Self-Healing Silicone Elastomers with Enhanced Mechanical Properties and Thermal Stability.

Photo-responsive materials have garnered significant interest for their ability to react to non-contact stimuli, though achieving self-healing under gentle conditions remains an elusive goal. In this research, an innovative and straightforward approach for synthesizing silicone elastomers is proposed that not only self-heal at room temperature but also possess unique photochromic properties and adjustable mechanical strength, along with being both transparent and reprocessable. Initially, aldehyde-bifunctional dithiophene-ethylene molecules with dialdehyde groups (DTEM) and isocyanurate (IPDI) is introduced into the aminopropyl-terminated polydimethylsiloxane (H2N-PDMS-NH2) matrix. Subsequently, palladium is incorporated to enhance coordination within the matrix. These silicone elastomers transition to a blue state under 254nm UV light and revert to transparency under 580nm light. Remarkably, they demonstrate excellent thermal stability at temperatures up to 100°C and show superior fatigue resistance. The optical switching capabilities of the silicone elastomers significantly affect both their mechanical characteristics and self-healing abilities. Notably, the PDMS-DTEM-IPDI-@Pd silicone elastomer, featuring closed-loop photo-switching molecules, exhibits a fracture toughness that is 1.3 times greater and a room temperature self-healing efficiency 1.4 times higher than its open-loop counterparts. This novel photo-responsive silicone elastomer offers promising potential for applications in data writing and erasure, UV protective coatings, and micro-trace development.

Adhesion and Transparency Enhancement between Flexible Polyimide-PDMS Copolymerized Film and Copper Foil for LED Transparent Screen.

With the increasing demand for innovative electronic products, LED transparent screens are gradually entering the public eye. Polyimide (PI) materials combine high temperature resistance and high transparency, which can be used to prepare flexible copper-clad laminate substrates. The physical and chemical properties of PI materials differ from copper, such as their thermal expansion coefficients (CTEs), surface energy, etc. These differences affect the formation and stability of the interface between copper and PI films, resulting in a short life for LED transparent screens. To enhance PI-copper interfacial adhesion, aminopropyl-terminated polydimethylsiloxane (PDMS) can be used to increase the adhesive ability. Two diamine monomers with a trifluoromethyl structure and a sulfone group structure were selected in this research. Bisphenol type A diether dianhydride is a dianhydride monomer. All three of the above monomers have non-coplanar structures and flexible structural units. The adhesion and optical properties can be improved between the interface of the synthesized PI films and copper foil. PI films containing PDMS 0, 1, 3, and 5 wt% were analyzed using UV spectroscopy. The transmittance of the PI-1/3%, PI-1/5%, PI-2/3%, and PI-2/5% films were all more than 80% at 450 nm. Meanwhile, the Td 5% and Td 10% heat loss and Tg temperatures decreased gradually with the increase in PDMS. The peel adhesion of PI-copper foil was measured using a 180° peel assay. The effect of PDMS addition on peel adhesion was analyzed. PIs-3% films had the greatest peeling intensities of 0.98 N/mm and 0.85 N/mm.

Migration of polydimethylsiloxane chain segments toward the surface of UV-cured waterborne poly(urethane-acrylate) films

Waterborne polyurethane (WPU) has poor water resistance and low surface hydrophobicity due to the incorporation of hydrophilic chain-extender. The water resistance and the surface hydrophobicity can be improved by incorporation of polydimethylsiloxane (PDMS), which is attributed to the migration of PDMS chain segments toward the surface of WPU film. However, whether the PDMS chain segments can migrate toward the surface of WPU film after UV-curing, resulting in higher hydrophobicity, needs further investigation? We prepared the different WPUA films by changing the molar ratio of aminopropyl-terminated polydimethylsiloxane (APT-PDMS) to hydroxyethyl acrylate (HEA), to deeply understand the migrating phenomenon of PDMS chain segments toward the surface of WPUA films. The migration cause of PDMS chain segments and the influence of chemical cross-linking on the migration were investigated by thermal annealing and solvent immersion of WPUA films. In addition, the migration activation energy and the relaxation time were studied by the migration rate of PDMS chain segments in the thermal annealing and the rheological behavior of WPUA film, aiming to elucidate the migration of PDMS chain segments depending on the chain motion and the fractional free volume. This investigation provides a simple and feasible strategy for improving the hydrophobicity of waterborne polyurethane.

The development of high‐strength, anticorrosive, and strongly adhesive polyaspartate polyurea coating suitable for pipeline spray repairs

AbstractThis study synthesized polydimethylsiloxane (PDMS)‐modified polyaspartate polyurea (PPPU) with different ratios, considering the practical performance requirements of underground water supply pipeline spray repair materials. The successful synthesis of PPPU was confirmed using Fourier transform infrared spectrometer (FTIR) spectroscopy. The influence of the ratio of the two components and the content of ‐aminopropyl terminated polydimethylsiloxane (APT‐PDMS) on the drying time and tensile performance of PPPU coatings was evaluated. Based on this evaluation, a superior ratio for PPPU coatings was proposed. Subsequently, the bonding performance, hydrophobicity, and corrosion resistance of PPPU coatings at the superior ratio were tested. The results indicate that as the mass ratio of polyaspartic acid ester to hexamethylene diisocyanate trimer increases, both the drying time and tensile strength of the coating decrease. The addition of APT‐PDMS results in a decrease in the tensile strength of PPPU, but an increase in its elongation at break. The peak value of elongation at break is achieved when the APT‐PDMS content is 5%, making the PPPU2‐1‐5 coating the superior ratio for spray application on water supply pipelines. Through experiments, it was determined that the bonding strength of the PPPU2‐1‐5 coating with cement mortar under dry and humid conditions, static water contact angle (93.4°), and corrosion resistance performance are superior to those of the unmodified polyurea coating, demonstrating its application advantages. The conclusions drawn in this study provide a theoretical foundation for the practical engineering application of PPPU.

Self-healing flexible strain sensor fabricated through 3D printing template sacrifice for motion monitoring with enhanced healing and mechanical performance

With the advancements in flexible materials and information technology, flexible sensors are becoming increasingly pervasive in various aspects of life and production. They hold immense potential for further development in areas such as motion detection, electronic skin, soft robots, and wearable devices. Aminopropyl-terminated polydimethylsiloxane (PDMS) was used as the raw material, while a diisocyanate reagent served as the cross-linking agent for the polymerization reaction, which involved the introduction of ureido groups, containing N–H and C=O bonds, into the long siloxane chain. The dynamic hydrogen bonding between the clusters completes the self-healing of the material. Using 1-[3-(trimethoxysilyl)propyl]urea as a grafting agent, the urea groups are introduced into graphene oxide and carbon nanotubes (CNTs) as conductive fillers. Subsequently, a flexible polymer is used as the substrate to prepare conductive flexible self-healing composites. By controlling the amount of conductive fillers, flexible strain materials with varying sensitivities are obtained. Design the structure of the flexible strain sensor using three-dimensional (3D) modeling software with deposition printing method.

Synthesis and Properties of Modified Biodegradable Polymers Based on Caprolactone.

In this paper, the synthesis and characterization of two polycaprolactone-polydimethylsiloxane (PDMS-CL) copolymers with biodegradable properties are reported. A comparative study was carried out using an aminopropyl-terminated polydimethylsiloxane macro-initiator (APDMS) with two different molecular weights. The copolymers (PDMS-CL-1 and PDMS-CL-2) were obtained by ring-opening polymerization of ɛ-caprolactone using APDMS as initiators and stannous 2-ethylhexanoate as a catalyst. The copolymer's structures were confirmed by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (1H-NMR) spectra, and energy dispersion spectroscopy (EDX). Surface morphology was investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The hydrophobic properties of the copolymers were demonstrated by the water contact angle and water vapor sorption capacity. Additionally, biological tests were conducted on San Marzano type tomato plants (Lypercosium esculentum) to assess the synthesized copolymers' susceptibility to the environment in terms of biological stability and metabolic activity. The biodegradation of PDMS-CL-1 and PDMS-CL-2 copolymers does not have a dangerous effect on the metabolic activity of plants, which makes it a convenient product in interaction with the environment.

Reinforcement of Aminopropyl-Terminated Siloxane-Treated Carbon Nanotubes in Epoxy Thermosets: Mechanical and Thermal Properties.

The synthesis and characterization of aminopropyl-terminated polydimethylsiloxane- treated carbon nanotube (AFCNT)-reinforced epoxy nanocomposites are reported in the current study. The amine functionalization of the CNTs was performed with a reaction to PDMS-NH2. The AFCNTs were homogeneously dispersed in epoxy resin by using an emulsifier and a three-roller mill. The AFCNTs were characterized using Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The curing behavior of the epoxy/AFCNT was studied using a differential scanning calorimeter (DSC). The tensile and impact strengths of the 2.0 wt.% AFCNT-reinforced epoxy nanocomposite were enhanced by 43.2% and 370%, respectively. Moreover, the glass transition temperature (Tg) was also enhanced by 21 °C. Furthermore, significant enhancements were observed in the initial degradation and char yield values. SEM results confirmed that the AFCNTs were highly dispersed in the polymeric matrix.

Interfacial rheology for probing the in-situ chemical reaction at interfaces of molten polymer systems

The design of new functional materials from immiscible polymers or multi-layered structures using reactive compatibilisation is an efficient approach that has been extensively employed in a wide range of applications. The adhesion/interfacial properties in these multiphase polymeric systems depend on the extent of reaction occurring at the interface. However, probing in-situ interfacial reactions in the molten state has proved challenging. In this study, interfacial shear rheology is used for the first time to directly probe the reaction at the interface between maleic anhydride-grafted polyethylene (PEgMA) and aminopropyl-terminated polydimethylsiloxane (PDMS-(PropNH2)2) used as model reactive polymer systems. Then the reaction at the interface was investigated using interfacial shear rheology based on a newly homemade, lightweight biconical setup. Thereafter, the time evolution of the interfacial tension with the progress of interfacial reaction was assessed using the pendant drop method. First, the extent of reaction was checked using differential scanning calorimetry (DSC) and dynamic rheology coupled with fast-scan FTIR spectroscopy. It has been demonstrated that the molecular weight of the aminated PDMS and the temperature of the medium markedly affect the rate of melt reaction at the interface and related interfacial rheological properties. Interestingly, the ability to assess the reactions at the interface in PEgMA/PDMS-(PropNH2)2 systems, even with low concentrations of reactive functionalities, demonstrates that interfacial rheology is a suitable, sensitive probe that could be applied to other reactive polymer systems, allowing better control of the resulting physical properties.

Effects of aminopropyl-terminated polydimethylsiloxane on structure and properties of waterborne polyurethane-acrylate

To achieve a good balance between mechanical properties and water resistance of the waterborne polyurethane (WPU) film, the hydroxylethyl acrylate (HEA) terminated waterborne polyurethane-acrylate (WPUA) emulsion was prepared by chain extension of 3,6-dioxa-1,8-octanedithiol (BOODT) and modification of aminopropyl-terminated polydimethylsiloxane (APT-PDMS). The effects of APT-PDMS on the microphase separation structure and the performance of WPUA film were investigated by varying the molar ratio of APT-PDMS to HEA. The introduction of APT-PDMS caused an increase in the content of hydrophobic groups, which could induce the rearrangement of the PDMS chain segments on the surface of WPUA during film formation. The rearrangement enhanced the surface hydrophobicity of WPUA, also improved the phase separation between hard and soft segments. The former was beneficial to obtaining better water resistance, while the latter was conducive to improving mechanical properties. However, the decrease in cross-linking degree will limit the mechanical properties and the water resistance with the increase in APT-PDMS/HEA molar ratio. The optimal balance between mechanical properties and water resistance can be achieved when the APT-PDMS/HEA molar ratio is 0.25. This work provides a feasible scheme for the industrial production of WPUA emulsions.

Mechanically Tough and Durable Poly(siloxane imide) Network Elastomer for Stretchable Electronic Applications

In the development of organic electronics, polyimide (PI)-based materials have drawn significant research attention due to their remarkable features, including a simple synthesis, solution processability, outstanding thermal stability, and respectable mechanical strength. Despite the good electronic performance of PI-based materials, a high elastic modulus over 1 GPa and a modest elongation at break of the conventional PIs have restricted their applications in stretchable electronics. To address this issue, poly(siloxane imide) (PSI) with a soft siloxane chain has been proposed to achieve a significantly reduced modulus and an increased stretchability. However, previous works revealed the weak mechanical strength of PSI, in which the latest reported stretchable device comprising PSI thin film could only sustain a tensile strain below 40%. Herein, in the present study, we developed a thermally stable and mechanically durable PSI network through the polyaddition–condensation reaction between 4,4′-oxidiphthalic anhydride, aminopropyl-terminated polydimethylsiloxane, and varied amounts of 1,3,5-triaminophenoxybenzene (TAB) as a cross-linker. An optimal PSI network with 11.1% TAB exhibited a high decomposition temperature at 426 °C, a softening temperature over 200 °C, an elongation at break over 400%, a superior toughness at 13.29 MJ m–3, and low strain hysteresis. Owing to the improved solubility of PSI, the polymer elastomer can be processed as a substrate material or thin-film active layer with good mechanical properties. Finally, all-solution-processed, stretchable, and durable electronic devices including resistive memory and organic field-effect transistors were fabricated using the designed PSI with an affordable and feasible solution process. This work underlines the importance of network design on soft polymers to create mechanically tough and durable elastomers for next-generation stretchable electronics.

A hydrophobic layer prepared by cyclic grafting of polydimethylsiloxane on magnesium: improved corrosion resistance and biocompatibility.

Magnesium and its alloys have been widely studied as absorbable coronary stent materials. However, the rapid corrosion rate in the intravascular environment inhibits the application of magnesium-based stents. In order to endow magnesium-based stent with appropriate degradation rate and biocompatibility, a hydrophobic layer was constructed by in situ cyclic grafting 4,4′-diphenylmethane diisocyanate and aminopropyl-terminated polydimethylsiloxane on pure magnesium. SEM-EDS, X-ray photoelectron spectroscopy and water contact angle were detected to analyze the chemical composition of the layer. The amino groups were confirmed to be introduced on the surface which provide a platform for subsequent modification. The contact angle value of the modified surface is 132.1°, indicating a hydrophilic surface. The electrochemical measurements and immersion tests demonstrated that the hydrophobic layer significantly improved the anti-corrosion ability of the substrate. Besides, the biocompatibility of the hydrophobic surface was examined by platelet adhesion, cytocompatibility in vitro and subcutaneous implantation in vivo. Immunological and histological results indicated that the hydrophobic layer had excellent biocompatibility. Therefore, the presented study might be a promising method for the surface modification of biomedical magnesium-based stent.

Conductive and room-temperature self-healable polydimethylsiloxane-based elastomer film with ridge-like microstructure for piezoresistive pressure sensor

The fabrication of piezoresistive pressure sensor with self-healing function has attracted worldwide attention for its great prospects in intelligent robots, remote health monitoring and electronic skin. In this work, a conductive and self-healable elastomer (CSE) film with ridge-like microstructure was designed for flexible piezoresistive pressure sensor. Firstly, self-healable polydimethylsiloxane (PDMS)-based elastomer with ureido and imine groups was synthesized via a simple one-pot two-step polycondensation reaction with aminopropyl-terminated PDMS, isophorone diisocyanate and 1, 3, 5-triformylbenzene as monomers. Secondly, the synthesized PDMS-based elastomer solution was casted onto a sandpaper pre-sprayed with ureido pyrimidinone grafted carbon nanotubes/polyurea mixed solution, and the CSE film was obtained after drying and peeling off from the sandpaper. The piezoresistive pressure sensor fabricated with two single-electrode CSE films exhibited high sensitivity of 8.7 kPa−1 (0–6.1 kPa), low detection limit (50 Pa), fast response capability (response/relaxation time of 40/117 ms) and repeatability for 10,000 loading–unloading tests. Moreover, the sensor was able to fully recover to normal work after healing for 36 h at room temperature or even 200 s under the irradiation of near infrared (NIR) light. Importantly, the sensor was successfully applied for not only detecting human motions including radial pulse, speech recognitions and joint movements but also monitoring health status wirelessly through Bluetooth transmission. Our findings put forward a novel method to fabricate a high-performance self-healable piezoresistive sensor for wearable electronics, healthcare monitoring and electronic skin.

Tannic Acid as a Natural Crosslinker for Catalyst-Free Silicone Elastomers From Hydrogen Bonding to Covalent Bonding.

The construction of silicone elastomers crosslinked by a natural crosslinker under a catalyst-free method is highly desirable. Herein we present catalyst-free silicone elastomers (SEs) by simply introducing tannic acid (TA) as a natural crosslinker when using poly (aminopropylmethylsiloxane-co-dimethylsiloxane) (PAPMS) as the base polymer. The crosslinked bonding of these SEs can be easily changed from hydrogen bonding to covalent bonding by altering the curing reaction from room temperature to heating condition. The formability and mechanical properties of the SEs can be tuned by altering various factors, including processing technique, the amount of TA and aminopropyl-terminated polydimethylsiloxane, the molecular weight and -NH2 content of PAPMS, and the amount of reinforcing filler. The hydrogen bonding was proved by the reversible crosslinking of the elastomers, which can be gradually dissolved in tetrahydrofuran and re-formed after removing the solvent. The covalent bonding was proved by a model reaction of catechol and n-decylamine and occurred through a combination of hydroxylamine reaction and Michael addition reaction. These elastomers exhibit good thermal stability and excellent hydrophobic property and can bond iron sheets to hold the weight of 500 g, indicating their promising as adhesives. These results reveal that TA as a natural product is a suitable “green” crosslinker for the construction of catalyst-free silicone elastomers by a simple crosslinking strategy. Under this strategy, TA and more natural polyphenols could be certainly utilized as crosslinkers to fabricate more organic elastomers by selecting amine-containing polymers and further explore their extensive applications in adhesives, sealants, insulators, sensors, and so forth.

Lubricant self-replenishing slippery surface with prolonged service life for fog harvesting

Slippery lubricant-infused surfaces exhibit excellent fog-harvesting capacities compared with superhydrophobic and superhydrophilic surfaces. However, lubricant depletion is typically unavoidable under dynamic conditions, and reinfused oil is generally needed to recover the fog-harvesting capacity. Herein, an effective strategy for delaying the depletion of lubricant to prolong the service life of fog harvesting is proposed. An ultrathin transparent lubricant self-replenishing slippery surface was fabricated via facile one-step solvent evaporation polymerization. The gel film of the lubricant self-replenishing slippery surface, which was embedded with oil microdroplets, was attached to glass slides via the phase separation and evaporation of tetrahydrofuran. The gel film GFs-150 (with oil content 150 wt% of aminopropyl-terminated polydimethyl siloxane (PDMS-NH2)) exhibited superior slippery and fog-harvesting performance to other gel films. Furthermore, the slippery surfaces with the trait of oil secretion triggered by mechanical stress exhibited better fog-harvesting capabilities and longer service life than surfaces without the function of lubricant self-replenishment. The lubricant self-replenishing, ultrathin, and transparent slippery surfaces reported herein have considerable potential for applications involving narrow spaces, visualization, long service life, etc.

A New Route to Highly Stretchable and Soft Inorganic–Organic Hybrid Elastomers Using Polydimethylsiloxane as Crosslinker of Epoxidized Natural Rubber

AbstractSulfur or peroxide crosslinking is the most common and conventional method to develop elastomeric materials. A new approach to crosslink epoxidized natural rubber (ENR) by aminopropyl terminated polydimethylsiloxane (AT‐PDMS) is described, intending to develop a new kind of hybrid organic–inorganic elastomers. The curing reaction is accelerated by using hydroquinone as a catalyst. The formation of the hybrid structure is evident from the appearance of two glass transition temperatures, at −1 and −120 °C, for the ENR and PDMS phases, respectively. The curing reaction is found to be of first order with respect to amine concentration with the estimated activation energy of ≈62 kJ mol−1. Comparing the mechanical properties to a typical ENR‐sulfur system leads to the conclusion that the ENR/AT‐PDMS hybrid structure is highly stretchable and soft, as demonstrated by its relatively higher strain at failure (up to ≈630%), and lower hardness and modulus values. The higher stretchability and soft nature of the material are achieved by introducing flexible PDMS chains during the curing process resulting to a hybrid elastomer networks. This kind of soft but robust materials can find several applications in diverse fields, such as soft robotics, flexible, and stretchable electronics.

Preparation and properties of propargyl ether-terminated poly(imide siloxane)s and their composites

The novel propargyl ether-terminated oligo(imide siloxane)s (PTISs) based on 2,2’-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), aminopropyl-terminated polydimethylsiloxane (APPS), 4,4’-diaminodiphenylmethane (MDA) and p-aminophenyl propargyl ether (APPE) were synthesized. The chemical structures of PTISs were characterized by proton nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectroscopy (FTIR). The PTISs exhibited excellent solubility in organic solvent and had broad processing window. The T300 carbon fabric was used to reinforce the PTIS matrices and prepare the composites (T300CF/PTISs). The thermal stability of the cured PTISs was analyzed by thermogravimetric analysis (TGA). The dynamic thermal mechanical properties of the composites were measured by dynamic thermomechanical analysis (DMA). The results show that the temperature at 5% weight loss (Td5) and residual yield at 800°C (Yr800°C) of the cured PTISs in N2 increase with incorporation of the aromatic diamine, whereas the Yr800°C of the cured PTISs in air decreases with introduction of the aromatic diamine. The elasticity of the composite increases with incorporation of the aromatic diamine, and the peak temperature of loss factor for the composites are higher than 300°C. The flexural strength, tensile strength and interlaminar layer shear strength (ILSS) of the T300CF/PTIS composite display the values of 439 MPa, 427 MPa and 32 MPa at room temperature, respectively. The retention of the flexural strength and ILSS for the T300CF/PTIS composite are above 80% at 250°C.

A novel type of self-healing silicone elastomers with reversible cross-linked network based on the disulfide, hydrogen and metal-ligand bonds

Herein, we report an innovative cross-linked network of silicone elastomer with good stretchability, thermal stability and autonomous self-healing. This type of elastomers was easily prepared by aminopropyl terminated polydimethylsiloxane (A-PDMS), thioctic acid (TA) and 2,6-pyridine dialdehyde (Py). As we know, TA was firstly incorporated into the reversible network of silicones to supply the dynamic disulfide bonds and endow the self-healing properties. Py was also introduced into the network which acted as the metal-ligand binding sites. Consequently, silicone elastomers with three different types of chemical interactions including the disulfide bonds, hydrogen bonds and metal-ligand bonds were obtained. Especially, they possessed good anticorrosion and strong adhesion affinity. We expected this type of silicone elastomers could be applied into the soft robotics, wearable electronics and stretchable circuit constructed.

Designed preparation of silicone protective materials with controlled self-healing and toughness properties

Silicone elastomers with adjustable self-healing and mechanical properties have been prepared by the step-by-step synthesis procedure that 4,4′-methylenebis-(cyclohexyl isocyanate) (HMDI) and isophthalaldehyde (IPAL) sequentially cross-linked with aminopropyl terminated polydimethylsiloxane (AP-PDMS). The characteristic imine and urea groups that related to self-healing ability and toughness have been detected in the silicone elastomers. The tensile stress of elastomers increases from ∼3 KPa to ∼1.0 MPa as increasing the ratio of urea to imine groups (0.35–3.3), while the elongation at the break still keeps in the range of 700−800 %. It was verified that the hydrogen bonding network exists in the self-healing polymers, which is responsible for its enhanced mechanical properties. The dynamic interaction of imine groups decreases with the increase of urea groups due to the limited movement of the polymer chain by hydrogen bonds, resulting in the degeneration of self-healing properties. Expectedly, the self-healing polymer (PDMS-UI-2) exhibits outstanding protective ability against corrosion of carbon steel in 3.5 % NaCl solution, owing to its rapid self-repairing property. Therefore, this work provides a facile and effective method to fabricate the self-healing silicon materials with adjustable self-repairing capability and mechanical property, which can be potentially used as protective coatings in the marine environment.

Fabrication of highly transparent and luminescent quantum dot/polymer nanocomposite for light emitting diode using amphiphilic polymer-modified quantum dots

Herein we present the fabrication of a highly transparent and luminescent quantum dot (QD)/polymer nanocomposite for application in optoelectronic devices. First, we encapsulated CdSe@ZnS/ZnS core/shell QDs with an amphiphilic polymer, i.e., poly(styrene-co-maleic anhydride) (PSMA). By encapsulating QDs with PSMA instead of ligand exchange, the photoluminescence intensity of the QDs could be preserved even after surface modification. Next, the PSMA-modified QDs were used as crosslinkers for the aminopropyl-terminated polydimethylsiloxane (PDMS) resin in a ring-opening reaction between the maleic anhydride of the QDs and the diamines of the PDMS, producing polymer networks at a low curing temperature. This method afforded a nanocomposite with uniform dispersion of QDs even at high QD concentrations (~30 wt%) and superior optical properties compared to a nanocomposite prepared from unmodified QDs and commercial resin. Owing to these enhanced properties, the nanocomposite was used to fabricate a light emitting diode (LED) device, and the luminous efficacy was found to be highest at 1 wt%.