Vinyl Functional Groups Research Articles

Controlled multi-vinyl monomer homopolymerization through vinyl oligomer combination as a universal approach to hyperbranched architectures

The three-dimensional structures of hyperbranched materials have made them attractive in many important applications. However, the preparation of hyperbranched materials remains challenging. The hyperbranched materials from addition polymerization have gained attention, but are still confined to only a low level of branching and often low yield. Moreover, the complication of synthesis only allows a few specialized monomers and inimers to be used. Here we report a 'Vinyl Oligomer Combination' strategy; a versatile approach that overcomes these difficulties and allows facile synthesis of highly branched polymeric materials from readily available multi-vinyl monomers, which have long been considered as formidable starting materials in addition polymerization. We report the alteration of the growth manner of polymerization by controlling the kinetic chain length, together with the manipulation of chain growth conditions, to achieve veritable hyperbranched materials, which possess nearly 70% branch ratios as well as numerous vinyl functional groups.

Simple Method to Fabricate an Biocompatible Antibacterial Surface on a Versatile Substrate through an Antiadhesion Approach

Abstract The synthesized polymer, poly(ethoxyethyl glycidyl ether-co-allyl glycidyl ether)-g-catechol (PEAC), has both vinyl and catechol functional side groups. Due to the pendant catechol groups, PEAC could be immobilized on various substrates tightly. Furthermore, the backbone of PEAC, poly(ethylene glycol), gives the PEAC-modified substrates good antiadhesion performance to bacteria. The antibacterial surface fabricated by this way is very different from the conventional method to empower material to have antibacterial properties directly or indirectly by killing bacteria absorbed.

Lactam derivatives as solid electrolyte interphase forming additives for a graphite anode of lithium-ion batteries

N-substituted caprolactam (CL) derivatives are examined as novel solid electrolyte interphase (SEI)-forming additives for improving the cycle performance of LiCoO2/graphite lithium-ion batteries (LIBs). Our electrochemical experiments and density function calculations reveal that N-substitution of acetyl, methyl, and vinyl functional groups to ɛ-CL greatly affects the oxidation/reduction reactions of the CL additives. The cyclability of LiCoO2/graphite cells are in the following order: acetyl–CL > ɛ-CL > methyl-CL > no additive > vinyl-CL. The cycle performance of acetyl–CL is comparable to that of VC, currently the most widely used SEI-forming additive in LIBs. The excellent performance of acetyl–CL is ascribed to the electron withdrawing nature of the acetyl group, which enhances the anodic stability and facilitates the reduction reaction, leading to superior SEI formation at the graphite anode.

Poly(N-isopropylacrylamide)-modified silica beads with hyperbranched polysiloxysilane for three-dimensional cell cultivation

The immobilization of poly(N-isopropylacrylamide) (PNIPAM) onto the surface of silica beads via hyperbranched polysiloxysilane (HBPS) was studied to develop a new material for cell cultivation. HBPS terminated with a vinyl functional group was synthesized by self-polymerization of an AB2 monomer. The terminal vinyl group was converted into a chain-transfer agent for reversible addition fragmentation chain transfer (RAFT) polymerization. The obtained HBPS was immobilized on the silica surface by mixing silica beads and HBPS in hexane. The graft polymerization of PNIPAM onto the silica surface was achieved using RAFT polymerization. The molecular weights of the grafted polymers obtained by cleavage from the surface of silica beads using NaOH aqueous solution were in the range of 6000–23 000 and the polydispersity index values were 1.4–1.6. The grafted silica beads have been tested for cell cultivation. Silica-HBPS-g-PNIPAM with a higher molecular weight (Mn) of PNIPAM (cleaved PNIPAM Mn=14 800 and 23 700) showed a thermo-reversible phase transition at approximately 34 °C, and controlled cell adhesion and detachment was demonstrated with these beads.

Synthesis of modified silica spheres used for the preparation of dual ultraviolet- and thermo-cured epoxyacrylate/silica composites

To investigate the interfacial effect on properties of epoxyacrylate–silica composites, submicron-sized silica spheres were synthesized by sol–gel reaction under a basic environment and their surfaces were endowed with vinyl functional groups by further modification with 3-methacryloxypropyl trimethoxy silane. The pure silica (PS) and the modified silica (MPS) spheres were characterized by Fourier transform infrared, 29Si- and 13C-nuclear magnetic resonance (NMR), scanning electron microscope (SEM), and particle size analyzer. The silica spheres were then added to the presynthesized difunctional epoxyacrylate resin with one vinyl group and one epoxide group at each end, in addition to the photo- and thermo-curing agents. After cure, thermal and mechanical properties of the obtained epoxyacrylate–silica composites were measured and compared. Tensile mechanical properties including initial modulus, ultimate tensile strength, and elongation at break, as well as the fracture energy of the epoxyacrylate–silica composite were all increased by increasing the content of silica spheres. Moreover, the composites filled with MPS had stronger interfacial strength between silica sphere and matrix than those with PS and thus exhibited an additional increase of tensile mechanical properties and fracture toughness. The increase of fracture toughness was owing to the crack deflection and particle–matrix debonding as evidenced by SEM pictures on the fracture surface. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

Addition of pyrroles onto terminal alkynes catalyzed by a dinuclear ruthenium (II) complex

The addition of pyrroles onto alkynes has been catalyzed by a dinuclear ruthenium complex, Ru2(CO)4(PPh3)2Br4, resulting in the formation of geminal 2-vinylpyrroles in high yields under mild conditions. Further functionalization with pyrroles or alkynes to afford dipyrrolmethanes or 2,5-bis(vinyl)pyrroles via the vinyl functional group can readily be achieved. A mechanism involving cationic ruthenium complexes was proposed based on the product regioselectivity, deuteration and infrared spectroscopic studies carried out on the catalytic process.

Annealing Influence on Siloxane-Based Materials Incorporated with Fullerenes, Phthalocyanines, and Silsesquioxanes

We have studied the heat treatment influence (room temperature to 400°C) on thin aminopropyltrimethoxysilane (APTMS)-based films incorporated with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), copper phthalocyanine (CuPc), and three-dimensional structure cage polyhedral oligomeric silsesquioxanes (POSS) by X-ray photoelectron spectroscopy and capacitance voltage technique. We discuss the interplay between the temperature degradation of the organic components (aminopropyl groups, sp3-based carbon bonds of APTMS, cyclopentyl rings, and vinyl functional group of POSS) and the thermal stability of the fullerene molecules (PCBM), benzene rings (CuPc), and the POSS inorganic cages. We observe the formation of Si–O–Si bridges between the POSS inorganic cages and the SiO2-enriched matrix which contains also fullerene molecules and benzene rings.

A general LbL strategy for the growth of pNIPAM microgels on Au nanoparticles with arbitrary shapes

A general method to encapsulate gold nanoparticles within thermoresponsive poly(N-isopropylacrylamide) (pNIPAM) shells is presented and demonstrated. The layer-by-layer (LbL) strategy was used to provide the metal nanoparticles surface with vinyl functional groups, from which pNIPAM can be readily grown. This method can be applied to the encapsulation of gold nanoparticles within a wide range of sizes, shapes and capping agents. We demonstrate here the encapsulation of cetyltrimethyl ammonium bromide (CTAB) stabilized Au spheres and poly(vinylpyrrolidone) (PVP) stabilized Au decahedra and nanostars, thereby exemplifying the fabrication of nanocomposites with tailored localized surface plasmon resonances (LSPR). Additionally, the total diameter of the Au@pNIPAM microgels, as well as the number of encapsulated metal cores, was varied through controlled addition of sodium dodecyl sulfate (SDS). The optical response could be thus modulated through temperature-induced local changes of the refractive index around the gold cores, as well as by plasmon coupling between metal nanoparticles located within the same microgel.

Ring-Opening Polymerization of γ-(4-Vinylbenzyl)-l-glutamate N-Carboxyanhydride for the Synthesis of Functional Polypeptides

Introducing various pendant functional groups and building blocks of interest to polypeptides in a highly efficient, controlled manner is crucial to access polypeptide materials with desired structures and functions. In this study, we synthesized γ-(4-vinylbenzyl)-(L)-glutamate N-carboxyanhydride (VB-Glu-NCA), which was readily obtained and purified in large quantity. VB-Glu-NCA monomer was subsequently used for the synthesis of polypeptides containing conjugation-amenable, pendant vinyl functional groups. Controlled, living polymerizations of VB-Glu-NCA were achieved by using hexamethyldisilazane (HMDS) as the initiator, catalytic amounts of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as the co-catalyst, and nitrobenzene as the inhibitor of radical-induced side reactions on the vinyl group of VB-Glu-NCA. The resulting poly(γ-(4-vinylbenzyl)-(L)-glutamate) (PVBLG) gave rise to polypeptides containing pendant functional groups or moieties through various vinyl chemistries.

Vinyl Functional Group Effects on Mechanical and Thermal Properties of Silica-Filled Silicone Rubber/Natural Rubber Blends

The silane (TESPD) treated silica-filled silicone rubber (SR)/natural rubber (NR) blends are studied with regard to their mechanical, thermal, and optical properties. Two grades of SR, with and without vinyl group are used and the results are compared. The effects of a vinyl functional group in SR with respect to vibration isolation property, and mechanical properties are investigated to find maximum torque, tensile strength, tensile modulus, elongation at break, hardness and tan δ. The compounds are cured with sulfur, peroxide and peroxide/sulfur combination. The results show that the presence of the vinyl group in SR helps improve the mechanical and thermal properties of the SR/NR blend. Scanning electron microscopy (SEM) photographs show that the silica particles are well dispersed in the rubber matrix. Thermal properties including thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and heat resistance are also studied. It shows the presence of the vinyl group in the SR/NR blend curing with the peroxide/sulfur combination improves both mechanical properties and the vibration properties.

Cellular compatibility of copolymer hydrogels based on site‐selectively‐modified chitosan with poly(N‐isopropyl acrylamide)

AbstractThis research synthesized graft copolymers of chitosan‐g‐poly(N‐isopropyl acrylamide) (CS‐g‐PNIPAAm) by UV‐initiated free‐radical polymerization of NIPAAm monomer to CS selectively at the C‐6 position of pyranose ring. First, amino groups in CS were protected by reaction with phthalic anhydride (PA) to form PACS. The degree of phthaloylation was carefully controlled to ensure that most amino groups were protected, and only a very small amount of hydroxyl groups were reacted. In the second step, the vinyl functional group was introduced to the PACS by reaction with a vinyl compound containing an isocyanate group (3‐isopropenyl‐αα′‐dimethylbenzyl isocyanate), through the urethane linkage with hydroxyl groups at the C‐6 position. The phthaloyl groups were then removed by hydrazine to recover the amino groups in CS. Finally, PNIPAAm was grafted to the vinyl CS at the C‐6 position by UV‐initiated free‐radical polymerization. The synthesized CS‐g‐PNIPAAm copolymers were confirmed to have a structure of an AB‐crosslinked graft copolymer. Respectively, these copolymer hydrogels exhibited pH‐ and thermal‐responsive swelling properties in an aqueous solution due to their CS and PNIPAAm components. The test of cell viability with L929 fibroblast revealed that the CS‐g‐PNIPAAm copolymers having a grafting ratio lower than 1.7 had cellular compatibility as good as pure CS. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Synthesis of hyperbranched polymers via a facile self-condensing vinyl polymerization system – Glycidyl methacrylate/Cp 2TiCl 2/Zn

A facile self-condensing vinyl polymerization (SCVP) system, the combination of glycidyl methacrylate, Cp 2TiCl 2 and Zn, has been firstly used to prepare novel hyperbranched polymers, consisting of vinyl polymers as the backbone, and cyclic ester polymers (poly(ɛ-caprolactone) or poly( l-lactide)) as the side chains. The polymerizations are initiated by the epoxide radical ring-opening catalyzed by Cp 2Ti(III)Cl which is generated in situ via the reaction of Cp 2TiCl 2 with Zn. The key to success is that the polymerizations can proceed concurrently via two dissimilar chemistries possessing the opposite active initiating species, including ring-opening polymerization (ROP) and controlled/living radical polymerization (CRP). We have demonstrated that this facile one-step polymerization technique can be applied successfully to prepare highly branched polymers with a multiplicity of end reactive functionalities including Ti alkoxide, hydroxyl and vinyl functional groups.

Reaction of di-2-chloroethyl 2-chloroethanephosphonate with potassium methacrylate

Reaction of di-2-chloroethyl 2-chloroethanephosphonate with potassium methacrylate at various component ratios was studied with the aim to prepare products containing methacrylate and vinyl functional groups. The structures of the compounds obtained were examined by 1H NMR and IR spectroscopy and by gas chromatography-mass spectrometry.

Rheological, thermal, and mechanical characterization of fly ash‐thermoplastic composites with different coupling agents

AbstractComposite materials were prepared by mixing fly ash obtained from biomass combustion as filler and isotactic polypropylene (PP) as matrix. Three silane‐type coupling agents mainly differing in the size of their functional groups were used to improve the compatibility between both components. Uniaxial tensile tests showed that the incorporation of untreated ash into PP led to stiffer but also more brittle and weaker materials, as Young's modulus significantly increased and tensile strength and elongation at break decreased. Furthermore, an enhancement in storage and loss moduli as well as in composite viscosity was observed with the addition of fly ash. Hardness tests and thermal and fracture surface analyzes revealed tensile test results similar to those mentioned earlier. In summary, after analyzing the effects of the three silanes on mechanical, thermal, morphological, and rheological properties, the silane containing the vinyl functional group (XL10) was selected as the most appropriate for the PP/ash composites investigated. POLYM. COMPOS., 31:1722–1730, 2010. © 2010 Society of Plastics Engineers.

In Situ Formation of Thermosensitive PNIPAAm-Based Hydrogels by Michael-Type Addition Reaction

To investigate the possibility of in situ thermosensitive hydrogel formation via Michael-type addition reaction, we designed and prepared thiol- and vinyl-modified poly(N-isopropylacrylamide) (PNIPAAm)-based copolymers. When the solutions of these two kinds of PNIPAAm-based copolymers were mixed at physiological temperature (37 degrees C), a physical gelation resulting from the hydrophobic aggregation of PNIPAAm based copolymers and chemical cross-linking between thiol and vinyl functional groups or so-called chemical gelation occurred, resulting in the formation of a three-dimensional hydrogel. Because all the gelations were performed at a high temperature (above LCSTs of the PNIPAAm based copolymers), these in situ formed hydrogels presented heterogeneous network structures, resulting in an improved thermosensitivity in comparison with the conventional one.

The effect of accelerated ageing on performance properties of addition type silicone biomaterials

The UV-protection provided to addition type silicone elastomers by various colorants, such as conventional dry earth pigments, as well as the so called "functional or reactive" pigments, was investigated. Moreover, the effect of a UV light absorber and a silica filler was also explored. Under the experimental parameters of this work, the exposure of silicone to UV radiation resulted in some changes of the IR absorbance, thermal decomposition after 400 degrees C, T(g) and tensile properties, whereas the storage modulus of samples was not affected. The obtained spectroscopic data, as well as the results of TGA and storage modulus, were interpreted by assuming that chain scission takes place during aging, whereas the improvement of tensile strength allows the hypothesis of a post-curing process, initiated by UV radiation. Therefore, the increase of T(g) could partly be due to the above reason and, furthermore, to the contribution of a rearrangement of chain fragments within the free volume of the elastomeric material. Regarding the evaluation of various coloring agents used in this work, the obtained results show that dry pigments are more sensitive to accelerated ageing conditions in comparison with functional liquid pigments. Moreover, the hydrophobic character of silicone matrix is enhanced, with the addition of this type pigments because of the vinyl functional silanes groups present in their chemical structure. Finally, it should be noted that the incorporation of silica nanofiller did not seem to prevent the silicone elastomer from degradation upon UV irradiation, but showed a significant reinforcing effect.

Superhydrophobic PLA fabrics prepared by UV photo-grafting of hydrophobic silica particles possessing vinyl groups

Superhydrophobic poly(lactic acid) (PLA) fabrics are prepared by UV photo-grafting of hydrophobic silica particles possessing vinyl functional groups on the surfaces, which is a novel one-step process to provide surface with roughness as well as hydrophobicity simultaneously. For this purpose, hydrophobic silica particles with vinyl groups and average diameter of 1.51 ± 0.05 μm are synthesized via a sol–gel process. The silica particles possessing vinyl groups are found to be effectively immobilized on PLA fabrics via UV photo-grafting reaction. The water contact angle of the treated PLA fabric is measured to be ∼150°, which is high enough to exhibit the Lotus effect as a result of the superhydrophobicity.

Synthesis and characterization of hyperbranched polymers via Cp2TiCl-catalyzed self-condensing vinyl polymerization using glycidyl methacrylate as inimer

Hyperbranched polymers were produced using glycidyl methacrylate (GMA)/Cp2TiCl2/Zn as self-condensing vinyl polymerization (SCVP) system. The polymerization is firstly initiated by the epoxide radical ring opening catalyzed by Cp2Ti(III)Cl generated in situ via the reaction of Cp2TiCl2 with Zn. By optimizing the molar ratio of the SCVP inimer (GMA) to the mediator (Cp2Ti(III)Cl), the active propagation chains are reversibly transformed to the dormant species and the cross-linking does not occur until a higher level of monomer conversion (ca. 80%). We detail this facile one-step polymerization technique to prepare highly branched polymers with a multiplicity of particular end reactive functionalities including Ti alkoxide, hydroxyl and vinyl functional groups, which differs from most previously reported SCVP systems.

Photoinduced reduction and heat-induced oxidation of silver in transparent RSiO3/2 and RSiO3/2–TiO2 films

Photoinduced reduction, resulting in nanoparticle formation, and heat-induced oxidation of doped silver have been demonstrated in silsesquioxane (RSiO(3/2)) and RSiO(3/2)-TiO(2) films (R = methyl, vinyl, and glycidoxypropyl) synthesized via the sol-gel method. The occurrence of redox behavior in the doped silver, i.e. formation and dissociation of silver nanoparticles (AgNPs) in the films, was confirmed by UV-Vis spectroscopy, IR spectroscopy, X-ray diffraction and transmission electron microscopy. The films containing vinyl and glycidoxypropyl organic functional groups were found to effectively reduce silver ions upon UV irradiation, whereas the film containing the methyl group substituent did not. Incorporation of a TiO(2) component into the RSiO(3/2) films caused thermal dissociation of the AgNPs. The formation and dissociation of AgNPs in the films was reversible by reiterating the cycle of UV irradiation and heat treatment.

Probing the assembly of highly vinyl-functionalized periodic mesoporous organosilica materials with crystal-like frameworks

Vinyl-functionalized periodic mesoporous organosilica materials (PMOs) with a crystal-like wall structure were synthesized, for the first time, by direct co-condensation of 1,4-bis(triethoxysilyl)benzene (BTEB) and triethoxyvinylsilane (TEVS). The synthesis approach led to high loading of vinyl functional groups and controlled regular morphologies. The resultant materials with different TEVS contents (up to 60 molar percentage) consisted of well-ordered mesopores (2.82-3.29 nm) with molecular-scale periodicity (7.6 A) in the walls, so that the high thermal stability of phenylene-bridged organosilica and versatile functionality of vinyl groups are combined. By exploring the influence of TEVS loading and the second monomer, tetraethoxysilane (TEOS), on the molecular-scale regularities, the rule of synergetic assembling of functional monosilylated TEVS and bissilylated BTEB was revealed. That is, the PMOs framework was built up only by BTEB, while TEVS was always terminally bonded to the channels surface.