Acrylic Acid Comonomer Research Articles

Thermo-sensitivity and erosion of chitosan crosslinked poly[N-isopropylacrylamide-co-(acrylic acid)-co-(methyl methacrylate)] hydrogels for application to the inferior fornix

Thermo-gels based on chitosan crosslinked poly(N-isopropylacrylamide) were developed as alternatives to conventional eye drops for the sustained release of ketotifen fumarate in the treatment of allergic conjunctivitis. The thermo-gelling properties of the base polymer were altered prior to crosslinking with chitosan by incorporation of the hydrophilic and hydrophobic comonomers acrylic acid and methyl methacrylate respectively. Varying amounts of chitosan were incorporated by ionic interaction to produce polyelectrolyte complexes or by carbodiimide chemistry to produce covalently crosslinked networks. The lower critical solution temperature of all the chitosan crosslinked thermo-gels produced was below the surface temperature of the eye. All the chitosan crosslinked thermo-gels were found to have greater than 80% equilibrium water contents following gelation. The method and amount of chitosan incorporation allowed for tailor-ability of material rheologic properties, with full degradation occurring over a one-to-four-day period, and tailorable rates of release of 40–60% of the loaded allergy medication ketotifen fumarate. The chitosan crosslinked thermo-gels were demonstrated to be nontoxic both in vitro and in vivo. It was demonstrated that the synthesized materials could be applied to the inferior fornix of eye, sustaining a multiple day release of ketotifen fumarate, as an alternative to conventional eyedrops. Statement of SignificanceTopical eyedrops are the main treatment modality for anterior ocular conditions. However, due to the natural clearance mechanisms of the eye, topical eyedrops are well established to be largely ineffective as a method of drug delivery. Herein, we investigate a method of altering thermo-gel properties of an n-isopropylacrylamide based polymer to enable the incorporation of greater amounts of chitosan by different methods of crosslinking. By controlling the synthesis parameters, final material properties can be tailored to impart ideal spreading, retention on the eye, and the rate of degradation and drug release over several days. This work also focuses on studying the rheological properties of the chitosan crosslinked thermo-gels which has not been investigated previously.

A sequential design approach for in situ incorporation of cellulose nanocrystals in emulsion-based pressure sensitive adhesives

Cellulose nanocrystals (CNCs) are naturally-sourced nanoparticles that can be used to modify polymers and provide exceptional mechanical properties to nanocomposite materials. In this study, CNCs were incorporated into water-based pressure sensitive adhesives (PSAs) via in situ semi-batch emulsion polymerization to improve PSA properties. A sequential design approach was used to improve CNC/poly(n-butyl acrylate/vinyl acetate) nanocomposite PSAs. In the first part of the design, the effects of acrylic acid (AA) and anionic surfactant sodium dodecyl sulfate (SDS) were examined in the presence of 0.5 wt% CNCs (based on polymer mass). While the SDS was crucial to maintaining latex stability, its excessive addition led to a decrease in PSA performance, namely tack and peel strength. The AA comonomer was pivotal in improving the shear strength of the PSAs, especially in the presence of CNCs. In all cases, the addition of CNCs led to improved PSA shear strength. In the second part of the design, the addition of 1-dodecanethiol (NDM) as a chain transfer agent (CTA) with CNC levels up to 1 wt% led to an improvement in tack and peel strength but at the cost of diminishing the shear strength. Generally, the addition of CNCs improved PSA performance. Thus, to maximize the impact of CNCs on PSA properties, a careful balance of SDS (for latex stability), AA (to improve shear strength) and NDM (to improve tack and peel strength) are needed.

Charged microgels adsorbed on porous membranes - A study of their mobility and molecular retention

The high flexibility of microgel synthesis provides a tremendous playground to tune properties of microgels, resulting in a broad variety of gels with tailor-made functionalities. Functionalized on membranes, microgels offer direct tuning of filtration properties of microgel-membrane composites. Regarding microgels as soft model colloids, the investigation of microgel-membrane interaction gives insight into the early formation of fouling layers and their stability. While it is known though that microgel properties strongly depend on the support, only few studies analyzed the behavior of microgels on porous surfaces as needed for membrane applications.In this study poly-(N-isopropylacrylamide) (PNIPAM) based microgels serve as soft model colloids. By successively increasing the concentration of the comonomer acrylic acid (AAc) we tune the charge of the microgels in neutral environment. We systematically study the transversal movement of the differently charged gels adsorbed on a porous polyethersulfone (PES) membrane as a function of convective flow and coating conditions. A 3D-printed online screening module allows us to observe single microgel movement under flow induced shear forces. The microgels exhibit a charge dependent mobility on the porous surface. We use the gained fundamental knowledge of microgel adsorption to achieve 65% retention of a charged dye on PNIPAM-co-AAc modified ultrafiltration and microfiltration membranes while neutral solutes pass.

Synthesis and characterization of cellulose based adsorbents for removal of Ni(II), Cu(II) and Pb(II) ions from aqueous solutions

Functional copolymers were prepared by graft polymerization of the cellulose extracted from agricultural residue rice husk thus represent a class of highly efficient, eco-friendly and biodegradable adsorbents for water purification applications. Functionalized grafted copolymers of cellulose with N-isopropylacrylamide (NIPAM) and comonomer acrylic acid (AAc) were synthesized by free radical grafting. To ascertain the grafting, cellulose and its graft copolymers were analyzed through various characterizations techniques such as FESEM, XRD, FTIR, TGA/DTA/DTG and swelling properties. Sorption of Ni(II), Cu(II) and Pb(II) metal ions was studied as a function of time, temperature, pH and concentration of metal ions in solution. The order for metal ions uptake was Cell-g-NIPAM-co-AAc > Cell-g-NIPAM > ungrafted cellulose. The metal ions sorption was best fitted in the pseudo-second-order kinetic model and Langmuir adsorption isotherm model. At the optimized conditions, almost complete sorption of Pb(II) ions was observed for Cell-g-NIPAM-co-AAc copolymer, whereas 74.5% of Ni(II) and 77.5% of the Cu(II) metal ions were sorbed by Cell-g-NIPAM-co-AAc copolymer.

Contribution of Surface Energy to pH-Dependent Underwater Adhesion of an Acrylic Pressure-Sensitive Adhesive.

Maintaining the underwater adhesive performance over a broad range of solution pH is challenging but necessary for many biomedical applications. Therefore, understanding how environmental conditions influence the mechanisms of bonding and debonding of pressure-sensitive adhesives (PSAs) can provide guidelines for materials design. We investigate how the presence of acrylic acid as aco-monomer impacts the adhesion of a model PSA in aqueous environments of varying pH. The adhesives under investigation are poly(2-ethylhexyl acrylate), or poly(2-EHA), and poly(2-EHA) co-polymerized with 5 wt % acrylic acid, or poly(2-EHA- co-AA). We characterize bonding and debonding (adhesion) of the adhesives using probe tack measurements with a spherical hydrophobic glass probe. We analyze the performance of the two PSAs in air and in low-ionic-strength buffered aqueous solutions of pH 3- 11. We find that the presence of theacrylic acid co-monomer increases the cohesiveness of the PSA and leads to stronger adhesion under all conditions investigated. We also observe that the presence of the acrylic acid co-monomer imparts the PSA with a strong dependence of adhesion on the solution pH. Dynamic contact angle and ζ potential measurements support the hypothesis that deprotonation of the acrylic acid groups at higher pH causes the decrease in adhesion at higher pH. Rheological measurements do not show changes in the dynamic mechanical properties of the PSAs after exposure to solutions of pH 3- 11. Our measurements allow us to isolate the effect of the solution pH on the surface and bulk properties of the PSA. In the absence of the acrylic acid co-monomer, the bulk dissipation and the surface properties of the PSA are independent of the solution's pH.

A Dirty Story: Improving Colloidal Monolayer Formation by Understanding the Effect of Impurities at the Air/Water Interface.

Colloidal monolayers are important tools to fabricate surface structures at the nanoscale. A typical monolayer fabrication strategy involves the self-assembly of colloidal building blocks at liquid interfaces, which are subsequently deposited on a solid substrate. Even though this process is well established, the resulting order of the particles within the colloidal monolayer differs between batches of colloidal particles and can even change with the age of the dispersion. In this study, we investigate the origins of this variation of monolayer quality for polystyrene particles synthesized by surfactant-free emulsion polymerization. We correlate the interfacial behavior of the colloidal particles at the air/water interface on a Langmuir trough with the resulting quality of the monolayer after transfer to a solid substrate. We identify surface-active impurities as a major cause for a disturbed self-assembly of the colloidal particles. These impurities form during the particle synthesis and consist of copolymers of styrene, the comonomer acrylic acid, and sulfonate species from the initiator. We show that they can be removed by cleaning protocols to increase the monolayer quality. However, our experiments demonstrate that the impurities reappear over time even for cleaned dispersions, indicating desorption from the surface of the colloidal particles. We identify strategies to avoid the presence of the impurities at the air/water interface or to inhibit their effect on the self-assembly process. These simple guidelines improve the quality of the resulting colloidal monolayer, which is a prerequisite for the reliable fabrication of high-quality surface nanostructures from colloidal templates.

Synthesis, characterization, and olefin (co)polymerization behavior of unsymmetrical α-diimine palladium complexes containing bulky substituents at 4-position of aniline moieties

Three novel unsymmetrical α-diimine Pd(II) complexes containing bulky substituents at 4-position of aniline moieties were prepared and characterized. Unfortunately, the introduction of large substituents on para- N-aryl moieties did not slow the exchange between the anti and syn forms for these complexes. These unsymmetrical α-diimine Pd(II) complexes also did not improve thermal stability and broaden molecular weight distribution in ethylene polymerization. However, these α-diimine palladium catalysts could copolymerize ethylene with biorenewable comonomer acrylic acid (AA), with comonomer incorporation in the range of 1.1–2.7% and high copolymer molecular weights. The AA units are incorporated predominately at the end of the branches. In addition, a systematic investigation on the polymerization of 1-hexene, 1-octene and 1-decene using these complexes was also performed. Changes in the ligand sterics and monomer length can influence the branch density and molecular weight of poly(α-olefins). Interestingly, these α-olefin polymers show properties characteristic of thermoplastic elastomers, i.e., good elastomeric recovery and high strain at break. Pervious work has shown that ethylene or α-olefin polymerization using some nickel α-diimine catalysts can generate elastic polyolefin materials. This work may provide an alternative and effective strategy to synthesize thermoplastic elastomers by α-diimine Pd(II) catalysts in one step using only α-olefin as the feedstock.

Sorption of Pb(II), Cu(II), Fe(II) and Cr(VI) metal ions onto cross-linked graft copolymers of chitosan with binary vinyl monomer mixtures

Novel adsorbents for sorption of Pb(II), Cu(II), Fe(II) and Cr(VI) metal ions from waste water were synthesized by simultaneous cross-linking and graft copolymerization of chitosan (Ch) with N-isopropyl acrylamide (NIPAM) and its binary comonomers acrylic acid, acrylamide and acrylonitrile in presence of azo-bis(isobutyronitrile) (AIBN) as free radical initiator and N,N′-methylene bisacrylamide (MBA) cross-linker. FTIR, XRD, SEM and TGA/DTA techniques were used to describe the structural aspects of cross-linked graft copolymers. The improvement in swelling properties of the synthesized hydrogels was utilized to explore their potential for sorption of toxic metal ions from aqueous solutions. Metal ion sorption by synthesized cross-linked adsorbents was studied as a function of the change in contact time, pH, temperature and concentration of metal ions from a solution of individual metal ions. Selective sorption of metal ions was performed by immersing polymeric samples in a solution containing four metal ions in the same concentration. Candidate polymers showed preferential sorption of metal ions in order of Cu(II)>Pb(II)>Fe(II)>Cr(VI) ions. Cross-Ch-g-poly(NIPAM-co-AAc), Cross-Ch-g-poly(NIPAM-co-AAm) and Cross-Ch-g-poly(NIPAM), showed best results for sorption of all ions from single and four component solutions.

Quantitative analysis on compressional behavior and swelling kinetics modeling of weakly ionic poly(N,N-dimethylacrylamide-co-acrylic/methacrylic acid or sodium acrylate) gels

A quantitative theoretical description of unusual elastic properties of rubbery materials in terms of the physico-chemical structural parameters remains a challenging task. The equilibrium and dynamic swelling properties of acrylamide-based ionic gels have been analyzed to optimize the design flexibility in terms of the molecular response, the structural integrity, and tunable diffusion behavior. A series of weakly ionic hydrogels and cryogels based on N,N-dimethylacrylamide (DMAAm) and the anionic comonomers acrylic acid (AAc), methacrylic acid (MAAc), and sodium acrylate (NaA) have been prepared by the crosslinking copolymerization using ammonium persulfate as initiator and N,N′-methylenebisacrylamide as crosslinker. By combining the swelling and elasticity data, quantitative agreement was demonstrated and the earlier qualitative observations was confirmed that both the effective charge density distribution and pKa value of weak polyelectrolytes can change substantially the responsive diffusion kinetics depending on the explicit account of charge association/dissociation of incorporated ionic comonomers. The swelling degree of ionic PDMAAm gels can sensitively respond to change in pH of the swelling media and the presence of ionic acrylic segments influences the swelling kinetics of the prepared gels evidently.

Direct Synthesis of Branched Carboxylic Acid Functionalized Poly(1-octene) by α-Diimine Palladium Catalysts.

In this work, we studied propylene polymerization using some α-diimine palladium catalysts with systematically varied ligand sterics. In propylene polymerization, the ligand steric effect exhibits significant variations on the catalytic activity, polymer molecular weight, and branching density. However, the regio control for the polymer microstructure is poor. Furthermore, copolymerization of 1-octene with the highly challenging and biorenewable comonomer acrylic acid was investigated. High copolymer molecular weights and high comonomer incorporation ratios could be achieved in this system. This study provides a novel access for the direct synthesis of branched carboxylic acid functionalized polyolefins.

Synthesis and characterization of graft copolymers of chitosan with NIPAM and binary monomers for removal of Cr(VI), Cu(II) and Fe(II) metal ions from aqueous solutions

To develop pH responsive hydrogels, N-isopropylacrylamide (NIPAM) has been grafted on to chitosan by free radical initiation method using azoisobutrylnitrile (AIBN) as an initiator. The optimum grafting conditions were worked out for grafting of NIPAM onto 1g of chitosan by varying one reaction parameter at a time and keeping all other parameters constant. Binary monomers were grafted for five different concentrations of comonomers acrylic acid (AAc), acrylamide (AAm) and acrylonitrile (AN) at optimum grafting conditions evaluated for GMA alone onto chitosan. The grafted copolymers were analyzed by FTIR, TGA/DTA, XRD and SEM. The swelling studies for the grafted samples were performed at various pH in order to explore their end use in sorption of Cr(VI), Fe(II) and Cu(II) ions from water system. Metal ion sorption behaviour of polymeric samples was studied as function of time, temperature and pH. Various metal ion sorption parameters such as percent uptake (Pu), partition coefficient (Kd) and retention capacity (Qr) were discussed. Chitosan grafted with binary monomers NIPAM-co-AAc and NIPAM-co-AAm showed best results for sorption of all three metal ions.

Gadolinium-Loaded Poly(N-vinylcaprolactam) Nanogels: Synthesis, Characterization, and Application for Enhanced Tumor MR Imaging.

We report the synthesis of poly(N-vinylcaprolactam) nanogels (PVCL NGs) loaded with gadolinium (Gd) for tumor MR imaging applications. The PVCL NGs were synthesized via precipitation polymerization using the monomer N-vinylcaprolactam (VCL), the comonomer acrylic acid (AAc), and the degradable cross-linker 3,9-divinyl-2,4,8,10-tetraoxaspiro-[5,5]-undecane (VOU) in aqueous solution, followed by covalently binding with 2,2',2″-(10-(4-((2-aminoethyl)amino)-1-carboxy-4-oxobutyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl) triacetic acid (NH2-DOTA-GA)/Gd complexes. We show that the formed Gd-loaded PVCL NGs (PVCL-Gd NGs) having a size of 180.67 ± 11.04 nm are water dispersible, colloidally stable, uniform in size distribution, and noncytotoxic in a range of the studied concentrations. The PVCL-Gd NGs also display a r1 relaxivity (6.38-7.10 mM-1 s-1), which is much higher than the clinically used Gd chelates. These properties afforded the use of the PVCL-Gd NGs as an effective positive contrast agent for enhanced MR imaging of cancer cells in vitro as well as a subcutaneous tumor model in vivo. Our study suggests that the developed PVCL-Gd NGs could be applied as a promising contrast agent for T1-weighted MR imaging of diverse biosystems.

In situ FTIR spectroscopy study on the rapid dissolution process of modified poly(vinyl alcohol)

In this article, modified poly(vinyl alcohol) (m-PVA) has been synthesized via copolymerization of vinyl acetate in methanol by adding comonomers acrylic acid and butyl acrylate followed by saponification. This modified poly(vinyl alcohol) can be completely dissolved into water before 60 °C without agitation. The rapid dissolution process of m-PVA was investigated by temperature-dependent Fourier transform infrared (FTIR) spectroscopy from 20 °C to 85 °C. The results showed that the wavenumber ranges of m-PVA in the O-H stretching and bending bands beyond the measuring range of the spectrometer were much larger than those of common PVA. This demonstrated that m-PVA chains could interact with water molecules more strongly and form hydrogen bonds with the hydroxyl groups of water more easily. The introduction of carboxyl groups destroyed the chemical regularity of polymer chains, which led to the decreasing crystallinity degree and imperfect crystal structures. Both the lower crystallinity degree and imperfect crystal structures were crucial factors to the rapid dissolution of m-PVA. Moreover, traditional Fourier transform infrared (FTIR) spectra, 1H nuclear magnetic resonance (1H NMR), and differential scanning calorimetry (DSC) were also applied to study the m-PVA in this paper.

Removal of safranine T and brilliant cresyl blue dyes from water by carboxy methyl cellulose incorporated acrylic hydrogels: Isotherms, kinetics and thermodynamic study

Polymer hydrogels having numerous functional groups can efficiently remove the low concentration of an industrial dye from water. This kind of functional adsorbent can be prepared by integrating a low cost polymer obtained from a naturally occurring polysaccharide such as sodium carboxy methyl cellulose (CMC) with a synthetic polymer like acrylic polymers. In the present work acrylic acid (AA)/N'N, methylene bis acrylamide(MBA), sodium acrylate/MBA and comonomers AA /hydroxyl ethyl methacrylate (HEMA)/MBA were free radical polymerized in an aqueous solution of CMC to produce several composite hydrogels. The swelling and dye adsorption properties of the hydrogels increased with an increase in the wt% of CMC. The hydrogels prepared with sodium polyacrylate and 6 wt% of CMC showed the highest swelling in water and also the highest adsorption (mg/g gel)/removal% of 9.45/94.5 and 9.89/98.9,respectively for 10 mg/L of Safranine T and brilliant cresyl blue dye, respectively, from water.

Investigation of pH-dependent swelling behavior and kinetic parameters of novel poly(acrylamide-co-acrylic acid) hydrogels with spirulina

AbstractPoly(acrylamide-co-acrylic acid)-spirulina (AAm-AAc-Sp) hydrogels were prepared by free radical solution polymerization of the monomer acrylamide (AAm) and the comonomer acrylic acid (AAc) with N,N-methylene bisacrylamide (BAAm) as the crosslinker in the presence of spirulina (Sp), which is a microalga species. The swelling ratios of the hydrogels were followed by gravimetric measurements. Hence, swelling kinetics and diffusion parameters were determined. Furthermore, the morphological structures and mechanical behaviors of the hydrogels were investigated by scanning electron microscopy and by using a uniaxial compression machine, respectively. All the results showed that spirulina had strong influence in the pH-dependent swelling behavior, as well as on the kinetic and diffusion parameters due to its interaction with the acrylic acid units. These interactions were attributed to spirulina, which caused a change in pore size and its distribution. The present novel hydrogels showed high swelling at neutral pH, but collapsed slowly at low and high pH values. Thus, these AAm-AAc-Sp hydrogels can be good candidates for pH-sensitive drug delivery systems.

Mechanical properties of a waterborne pressure-sensitive adhesive with a percolating poly(acrylic acid)-based diblock copolymer network: Effect of pH

Copolymerizing an acrylic acid comonomer is often beneficial for the adhesive properties of waterborne pressure-sensitive adhesives (PSAs). Here, we demonstrate a new strategy in which poly(acrylic acid) (PAA) is distributed as a percolating network within a PSA film formed from a polymer colloid. A diblock copolymer composed of PAA and poly(n-butyl acrylate) (PBA) blocks was synthesized using reversible addition–fragmentation chain transfer (RAFT) polymerization and adsorbed onto soft acrylic latex particles prior to their film formation. The thin adsorbed shells on the particles create a percolating network that raises the elastic modulus, creep resistance and tensile strength of the final film. When the film formation occurs at pH 10, ionomeric crosslinking occurs, and high tack adhesion is obtained in combination with high creep resistance. The results show that the addition of an amphiphilic PAA-b-PBA diblock copolymer (2.0wt.%) to a soft latex provides a simple yet effective means of adjusting the mechanical and adhesive properties of the resulting composite film.

Ultrasoft, highly deformable microgels.

Microgels are colloidally stable, hydrogel microparticles that have previously been used in a range of (soft) material applications due to their tunable mechanical and chemical properties. Most commonly, thermo and pH-responsive poly(N-isopropylacrylamide) (pNIPAm) microgels can be fabricated by precipitation polymerization in the presence of the co-monomer acrylic acid (AAc). Traditionally pNIPAm microgels are synthesized in the presence of a crosslinking agent, such as N,N'-methylenebisacrylamide (BIS), however, microgels can also be synthesized under 'crosslinker free' conditions. The resulting particles have extremely low (<0.5%), core-localized crosslinking resulting from rare chain transfer reactions. AFM nanoindentation of these ultralow crosslinked (ULC) particles indicate that they are soft relative to crosslinked microgels, with a Young's modulus of ∼10 kPa. Furthermore, ULC microgels are highly deformable as indicated by a high degree of spreading on glass surfaces and the ability to translocate through nanopores significantly smaller than the hydrodynamic diameter of the particles. The size and charge of ULCs can be easily modulated by altering reaction conditions, such as temperature, monomer, surfactant and initiator concentrations, and through the addition of co-monomers. Microgels based on the widely utilized, biocompatible polymer polyethylene glycol (PEG) can also be synthesized under crosslinker free conditions. Due to their softness and deformability, ULC microgels are a unique base material for a wide variety of biomedical applications including biomaterials for drug delivery and regenerative medicine.

Grafting of GMA and some comonomers onto chitosan for controlled release of diclofenac sodium

In order to develop pH sensitive hydrogels for controlled drug release we have graft copolymerized glycidyl methacrylate (GMA) with comonomers acrylic acid, acrylamide and acrylonitrile, onto chitosan (Ch) by using potassium persulphate (KPS) as free radical initiator in aqueous solution. The optimum percent grafting for GMA was recorded for 1g chitosan at [KPS]=25.00×10−3mol/L, [GMA]=0.756×10−3mol/L, reaction temperature=60°C and reaction time=1h in 20mL H2O. Binary monomers were grafted for five different concentrations at optimum grafting conditions evaluated for GMA alone onto chitosan. The graft copolymers were characterized by FTIR, XRD, TGA and SEM. The swelling properties of chitosan and graft copolymers were investigated at different pH to define their end uses in sustained release of an anti-inflammatory drug, diclofenac sodium. Percent drug release w.r.t. drug loaded in polymeric sample was studied as function of time in buffer solutions of pH 2.0 and 7.4. In vitro release data was analyzed using Fick's Law. Chitosan grafted with binary monomers, GMA-co-AAm and GMA-co-AN showed very good results for sustained release of drug at 7.4 pH.

Luminescence properties of polymers containing europium complexes with 4-tert-butylbenzoic acid

The binary europium complex EuL3 (L=4-tert-butylbenzoate) and ternary europium complexes EuL3TTA0.1 (TTA=2- thenoyltrifluoroacetone), EuL3DBM0.5 (DBM=dibenzoylmethane) and EuL3phen0.5 (phen=1, 10-phenanthroline) were synthesized. The poly(methyl methacrylate) (PMMA) or copolymer of methyl methacrylate (MMA) with acrylic acid (AA) composites doped with europium complexes were prepared by radical in-situ polymerization. The influences of the europium complexes, ligands, N,N-dimethylformamide (DMF) and monomers on the luminescence properties of the doped polymers were investigated. The results showed that the fluorescence excitation bands of binary and ternary complexes were in accordance with their ultraviolet absorption bands. All the complexes and the doped polymer composites exhibited the ligand-sensitized red characteristic emission of Eu3+ ion. The fluorescence intensity of the polymer composites increased in the sequence of EuL3/PMMA<EuL3phen0.5/PMMA<EuL3DBM0.5/ PMMA<EuL3TTA0.1/PMMA. It indicated that the introduction of a small amount of β-diketone ligand affected the optimum excitation wavelength and the fluorescence intensity of polymer composites. Furthermore, DMF remarkably increased the luminescence intensity and transparence of the doped polymer composites. However, introduction of acrylic acid comonomer decreased the luminescence intensity of the polymer composites.

Preparation of polystyrene/poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylenevinylene] fluorescent microspheres by miniemulsion polymerization

Fluorescent microspheres have great potential for use as probes in biological diagnostics. In this context, poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV), a conjugated polymer which has high quantum yield, controllable emitting wavelength and facile processing in manufacture, was used as a fluorescent material for the preparation of polystyrene (PS)/MEH-PPV fluorescent microspheres via miniemulsion polymerization. We demonstrate that the emitting wavelength of the PS/MEH-PPV fluorescent microspheres can be regulated by changing the amount of azobisisobutyronitrile initiator in the polymerization process. Using acrylic acid comonomer, poly[styrene-co-(acrylic acid)]/MEH-PPV fluorescent microspheres with functional carboxyl groups were also prepared. All the microspheres were characterized using transmission electron microscopy, scanning electron microscopy, fluorescence microscopy and fluorescence spectrophotometry. The functional carboxyl groups were characterized using Fourier transform infrared spectroscopy. This work provides a novel platform for the preparation of conjugated polymer fluorescent microspheres for biological applications. © 2012 Society of Chemical Industry