Multifunctional Comonomers Research Articles

Preparation and Properties of Graphene/ODA-PMDA-NTADA Copolyimide Nanocomposites Based onKH550-modification

In this study, KH550-modified graphene/ODA-PMDA-NTADA copolyimide nanocomposites were successfully made in an organic medium using KH-550 chemically modified reduced graphene oxide (rGO-NH2) as a multi-functional comonomer combinied with commercially available ODA, PMDA, and NTADA monomers, and their dispersive, morphological, thermal, viscous, conductive properties were investigated. Compared to pure PI, the dispersion compatibility, thermal characteristics and electrical conductivity of the produced nanocomposites were improved significantly. The improved rGO/PI nanocomposites showed more than 20 °C and 10 °C increase of Td5% and Td10% values respectively. This research demonstrates a facile and efficient method for creating homogeneous and multi-functional PI-based engineering materials and advanced functional materials.

Molecule control and thermal degradation study of phosphazene cyclomatrix nanocrystals: For simultaneous enhancement of flame retardant and mechanical properties

Cyclotriphosphazene which possesses hexafunctional framework is a versatile building block to construct functional materials and has been used in many areas such as catalysis, biomedicine, sensing and imaging, and flame retardancy. However, the proper control of the molecules and their condense state structures, in particular via the reaction of phosphonitrilic chloride trimer (PCT) with other multifunctional co-monomers is a challenge. Herein, we developed phosphazene cyclomatrix molecules using pentarythritol (PER) as the co-monomer. Through controlling the PCT/PER molar ratio and the feeding manner, the obtained product is either monomeric/oligomeric small molecules or macromolecules. Interestingly, the macromolecules self-assembled into three-dimensional structures, forming cubic nanocrystals. The thermal study shows that all molecules possess a low temperature degradation domain (LTD, 150–400 °C) and high temperature degradation domain (HTD, 500–750 °C) due to the same chemical bonds, while the macromolecules have the highest carbon forming among all. TG-IR and TG-MS results confirm the following thermal degradation features: (1) inert gases (NH3, CO2) and H2O release after 200 °C, (2) the carbonaceous phase forms at 300–450 °C when the PER segment content in the molecule is 50 % and higher, and (3) extra phosphate/phosphite agents release after 450 °C, which renders carbonizing capability. The addition of the crystalline macromolecules into polypropylene (PP) showed that under a low loading of only 18 and 22 wt%, UL94 V2 and V0 rate was achieved for the obtained composites. This indicates the high flame retardant efficacy of the macromolecules as a standalone additive, ascribing to the cooperative effect of the above thermal features in a single molecule. The synthesized macromolecule is also able to simultaneously reinforce PP in terms of tensile modulus and flexural modulus without sacrificing the impact strength and flexural strength, leading to dual functionality, i.e., enhancement flame-retardant (FR) performance and mechanical reinforcement. This study provides constructive guideline to controllably design and synthesize functional materials using this unique building block for advanced properties and applications.

Synthesis of Biocompatible and Biodegradable Polyamidoamines Microgels via a Simple and Reliable Statistical Approach.

Polyamidoamines (PAAs) are biocompatible and biodegradable polymers with a huge potential as biomaterials for pharmaceutical applications. They are obtained by the step-wise aza-Michael polyaddition of bifunctional or multifunctional amines with bisacrylamides in water. To the best of our knowledge, no synthetic protocols leading to hyperbranched PAAs as well as PAA microgels have been published so far. To fill this gap, a statistical approach was established in this work to fine-tune the aza-Michael polyaddition stoichiometry when a multifunctional co-monomer (bf) is added to a mixture of bifunctional monomers with complementary functions (a2 + b2), possibly even in presence of a monofunctional co-monomer (b1), for obtaining either microgels or hyperbranched polymers by a one-pot reaction. For this purpose, two new equations, obtained by reworking the classic Flory–Stockmayer equations, were successfully applied to the synthesis of different model systems, obtaining biocompatible microgels with tunable size distribution (200–500 nm) and properly designed end-chains in a simple and straightforward way. The same mathematical approach allowed us to empirically evaluate the actual number of active reactive functions of the co-monomers. A number of selected systems, being evaluated for their cytotoxicity in vitro, proved highly cytocompatible and, therefore, endowed with great potential for pharmaceutical and medical applications.

Histocompatibility of Dental Restorative Composite Resin Photopolymerized with a Novel Multifunctional Comonomer: A Histopathological Analysis in Rats.

Background:Restorative dentistry is impossible without composite resins. Toxicity of these resins is common though possessing favorable properties. Modifications of the resin matrix are being executed to improve the properties of the material. Dipentaerythritol penta-/hexa-acrylate (DPEPHA) monomer has been recently identified as a cross-linking comonomer with the conventional resin matrix.Purpose:This study aimed to investigate the histocompatibility of DPEPHA comonomer in photopolymerized resin at 20 and 40 wt.% concentrations in rats.Materials and Methods:Eighteen male Wister rats were subjected to subcutaneous implantation of conventional resin specimens without DPEPHA (G0) and with DPEPHA at 20 wt.% (G20) and 40 wt.% (G40) concentrations. Then, the rats were subdivided according to the time of resection of the implantation sites at 1, 2, and 4 weeks (n = 6 rats). Tissue specimens were submitted to histopathological analysis.Results:Except for 4 weeks' time interval, there were significant differences (P < 0.05) in the inflammation among the groups at each time interval. The order of inflammation was NC <G40 ≤G20 <G0. Concerning the fibrous capsule thickness, significant difference existed among the groups at each time interval and within the groups at all 3 time intervals (P < 0.05).Conclusion:Composite resin specimens with DPEPHA comonomer exhibited good histocompatibility in rats at 40 wt.% concentration.

Scale-up one-pot synthesis of waste collagen and apple pomace pectin incorporated pentapolymer biocomposites: Roles of waste collagen for elevations of properties and unary/ ternary removals of Ti(IV), As(V), and V(V)

Herein, hazardous solid particulate waste collagenic fibers (SWCFs) of leather industries were incorporated into apple pomace pectin (APPN)-grafted-pentapolymer, i.e., APPN-g-[sodium 2-methylidenebutanedioate(SMBD)-co-N-((3-(isopropylamino)-3-oxopropoxy) methyl) butyramide (CM1)-co-N-(hydroxymethyl)prop-2-enamide (NHMPE)-co-N-(hydroxymethyl)-4-(N-isopropylbutyramido)butanamide (CM2)-co-N-(propan-2-yl)prop-2-enamide NPYPE)/ PENP1], i.e., APPN-g-PENP1/ PENP2, prepared via one-pot facile polymerization of APPN and synthetic monomers, i.e., SMBD, NHMPE, and NPYPE, in aqueous medium, to fabricate an optimum multifunctional hybrid biocomposite adsorbent/ HCOM3. In PENP1, PENP2, and HCOM3, fourth/ CM1 and fifth/ CM2 multifunctional comonomers were anchored in situ. The structures of PENP1, PENP2, HCOM3, CM1, CM2, and metal-ion adsorbed HCOM3; APPN-grafting; SWCF incorporation; and surface properties were analyzed through NMR, XPS, FTIR, XRD, and SEM. The elevated adsorption efficiencies (AEs), reusability, thermostability, swelling, network durability, and crosslink density of HCOM3 were attributed to variable functionalities of SWCF/ APPN, explored by DLS and TGA, swelling, network, and thermodynamic parameters. Compared to SWCF, APPN, PENP1, and PENP2, the elevated AEs and reusability compelled HCOM3 as more suitable for scalable waste management. The maximum AEs, i.e., 171.79, 180.47, and 177.27 mg g–1, for Ti(IV), As(V), and V(V) at pHop = 7.0, 3.0, and 5.0, respectively, within 5–100 mg L–1 and at 298 K for 25 mg HCOM3 deteriorated during ternary adsorption by the antagonistic effects.

Super Porous Hydrogels

Super porous hydrogel (SPH) swells very rapidly in a shorter period of time (due to the presence of interconnected microscopic pores) to an equilibrium size and contains highly porous structure. Hydrogels are they are water insoluble. The swelling properties of hydrogels are mainly related to the network elasticity, the presence of hydrophilic functional groups, the cross-link density, and porosity. The first approach for SPH synthesis involves cross-linking of co-monomers using multifunctional co-monomer, which acts as cross-linking agent. They maintain their integrity in the harsh stomach environment, while releasing the pharmaceutical active ingredient. The fast swelling property is based on water absorption through open porous structure by capillary force. The retention of the dosage form in the stomach prolongs overall GI transit time, thus resulting in improved oral bioavailability of the drug. Because these hydrogels absorb a large volume of environmental fluids, which expand their volume considerably over a very short time, their sheer bulk hinders their transport to the next organ via the narrow pylorus. This unique swelling property allows them to be used as gastric retention carriers, providing sustained release through long/maximium residence in the stomach region.

Facile and cost-effective branched acrylic copolymers from multifunctional comonomers and multifunctional chain transfer agents

Branched acrylic copolymers were synthesised via facile conventional free-radical polymerisations taken to high conversion using comonomers containing 2-6 acrylate functional groups and chain transfer agents containing 1-8 thiol functional groups.

Improved compressive strength of poly(p-phenylene benzobisoxazole) copolymer fiber containing multi-functional comonomer

Multi-functional comonomer from pentaerythritol (PE) and terephthaloyl chloride (TPC) was synthesized and used for polymerization of poly(p-phenylene benzobisoxazole) (PBO) copolymer. PBO copolymer fibers were prepared from PBO copolymers using a dry-jet wet spinning. The tensile strength of PBO copolymer fibers was higher than that of PBO, and showed 42 % increase at 0.5 mol% loading of comonomer. The tensile modulus of PBO copolymer fiber at 0.5 mol% loading showed 192 % increase compared to PBO fiber. The compressive strength of PBO copolymer fiber had values between 0.46 GPa and 0.6 GPa with the comonomer content. 64-114 % increase in compressive strength of PBO copolymer fibers was observed compared to PBO fiber.

Bio-based semi-aromatic polyesters for coating applications

Linear and branched bio-based semi-aromatic (co)polyesters were evaluated as resins for solvent-based and powder coatings. Dimethyl-2,5-furandicarboxylate (DMF), 2,3-butanediol and various multifunctional comonomers were used to synthesize amorphous hydroxyl-end-capped (co)polyesters. The resins were cross-linked using the ɛ-caprolactam blocked trimer of isophorone diisocyanate. Both the solvent-based and powder coatings proved to be hard but brittle, which was a result of the very stiff molecular structure of the formed network. This was corroborated by the Tg values obtained for the coatings, which exceeded 100°C for both the solvent-based and powder coatings. The poly(ester urethane) coatings prepared from the branched copolyesters show a reasonable solvent resistance. However, swelling occurred during the solvent treatment, indicating an insufficient network formation. The solvent-based and powder coatings exhibit similar mechanical and physical performance, showing that in this study there was no significant influence of the preparation method. In view of the obtained results it can be concluded that DMF-based branched polyesters are interesting candidates for solvent-based and powder coating applications.

Branched poly(methyl methacrylates) modified by C60 fullerenes

The poly(methyl methacrylates) of branched structure with a covalently bonded fullerene were synthesized by three-dimensional radical polymerization of methyl methacrylate with triethylene glycol dimethacrylate or allyl methacrylate in toluene containing C60. The kinetics of copolymerization of methyl methacrylate with multifunctional co-monomers in the absence of fullerene is compared with that in its presence. The physicochemical characteristics and thermal stability of the obtained copolymers are also compared. The electron spin resonance (ESR) method was applied to study the kinetics of accumulation of the fullerene radicals in the course of the (co)polymerization of methyl methacrylate.

Modeling Free Radical Ethylene Polymerization with Multifunctional Comonomers in Tubular Reactors: Influence on Microstructural LDPE Properties

AbstractSummary: A kinetic model is developed to predict the effect of multi‐functional comonomers in the high‐pressure polymerization of ethylene in industrial tubular reactors. Two different modified acrylate based comonomers were tested in the simulation for their influence on molecular‐weight distribution and branching densities. A comparison of both methods shows their potential to be used in an industrial process.

Design and synthesis of three-dimensional hydrogel scaffolds for intervertebral disc repair

Intervertebral disc degeneration is a major cause of low back pain, which affects a large proportion of the population. Spinal fusion is one of the common solutions to restrict motion and stabilize, however biomechanical changes cause further problems. Although tissue engineered IVD structures and cell based therapies are being developed it is crucial that the structures are able to support spinal load. In this paper we report a biomaterial based regenerative approach with the first stage being the synthesis and characterisation of a group of hydrogels that has the potential to be further developed for cell-biomaterial based approaches. Copolymers of 2-hydroxyethylmethacrylate and a multifunctional comonomer, pyromellitic glycerol dimethacrylate p(HEMA/PMGDM) were synthesized and the effects of composition on the thermal behaviour and dynamic mechanical behaviour of these copolymeric hydrogels and the feasibility of use as biomaterials for IVD are reported. The HEMA-co-PMGDM copolymeric networks were shown to have highly controllable viscoelastic properties; the presence of a strong beta transition in the glassy region (in vivo temperature range) and the energy absorption and dissipation of the system (critical to disc function) could be easily controlled by tailoring the copolymer composition, crosslinking agent concentration and polymerisation methods, which is of great significance for the end use of these materials, as the essential function of the gelatinous nucleus is to resist, dampen and redistribute mechanical forces within the spine outwards towards the constricting annulus. To date there is no previous research incorporating PMGDM into hydrogel systems for biomedical applications.

Branched methacrylate copolymers from multifunctional comonomers: the effect of multifunctional monomer functionality on polymer architecture and properties

Soluble, branched (meth)acrylic copolymers have been synthesised via facile, one-step, batch solution polymerisations taken to high conversion. Methyl methacrylate has been copolymerised with a number of multifunctional comonomers using a chain transfer agent to prevent gelation. A variety of soluble, branched copolymer architectures have been synthesised using multifunctional monomers containing between two and six acrylate functional groups. Independent of polymer composition, all copolymers were proven to be branched with broader molecular weight distributions compared to linear analogues. The molecular weights, Mark–Houwink constants and Tg's all varied systematically depending on the functionality and concentration of the multifunctional monomer copolymerised. Although the polymer architectures are complex, this methodology is pragmatic, highly practical and very convenient. The need for high control of polymer architecture via controlled radical polymerisation for satisfying applications is questioned. It is proposed that precise control may not be necessary for many applications, whereas new, heterogeneous structures via pragmatic routes may be sufficient and more easily exploited.

Microporous polypropylene hollow fiber membranes: Part II. Pervaporation separation of water/ethanol mixtures by the poly(acrylic acid) grafted membranes

Polypropylene hollow fiber membranes grafted with poly(acrylic acid) were used for water–ethanol separation by pervaporation. The effects of grafting degree of poly(acrylic acid) (PAA), the cross-linking degree of the grafted-PAA, the sodium counter-ions as well as the operation temperature and the ethanol concentration in feed mixtures on pervaporation properties were investigated. It was found that water-permselective pervaporation membranes could be prepared by the grafting polymerization of acrylic acid on microporous polypropylene hollow fiber membrane surface. The separation factor increased with the increase of grafting degree of PAA in the range of 20–70 wt.%. Incorporating counter-ions as well as multifunctional comonomer into the grafted chains could improve the selectivity but sacrificed the permeation flux. The separation factor of the counter-ion containing membrane decreased according to the sequence Al 3+ > K + > Ca 2+ > Na + > Li + and the permeation flux increased following the sequence Al 3+ < Ca 2+ < K + < Na + < Li +. Remarkable increase in permeation flux without decrease in separation factor was observed for Al 3+ as counter-ion in this membrane. These results might be ascribed to the increase of packing density and the decrease of swelling degree of grafted layer on the membrane surface.

Application of multifunctional base monomer to dental composite resins

Experimental composite resin systems were prepared with visible-light-cured multifunctional matrices to which various amounts of organic composite filler were added. In comparison with the unfilled resins, the filled resin systems were tested for Knoop hardness, compressive and diametral tensile tests, thermal properties, and water sorption. Analyses of the results obtained for the unfilled resins indicate that the increased hardness and mechanical strength were dependent on the multifunctional base monomer. The effective composite resin system was the one that was filled with organic composite filler in the multifunctional comonomer having triethylene glycol dimethacrylate as a diluent monomer.

Behaviour of crosslinked polymers

For application as components in an adhesive layer in photographic movie-films, five copolymers of methylmethacrylate and butylacrylate each with a different multifunctional comonomer, have been synthetized. Depending on the copolymerizability of the multifunctional comonomers, adhesive layers with different mechanical properties were obtained. An approach towards an explanation for the diverging results from swelling and modulus measurements was worked out.