Acrylate Methacrylate Copolymers Research Articles

Degree of cure of orthodontic composite attachments underneath aligners.

The aim of this study was to assess the percentage degree of cure (DC%) of 2-mm-thick resin composite attachments used for aligner treatment. Three types of aligner - two thermoformed aligners (Clear Aligner [CLA], polyethylene terephthalate glycol modified; and Invisalign [INV], polyester urethane) and a three-dimensional-printed aligner (Graphy TC-85DAC [GRP], an acrylate-methacrylate copolymer) - were selected, along with two universal resin composites (3M Filtek Universal [FTU] and Charisma Topaz ONE [CTO]). Samples of each composite were placed under each aligner, and the degree of cure of each composite was evaluated on the top (facing the aligner) and the bottom (facing the substrate) attachment surfaces after curing. Five specimens were used per combination of aligner and composite, and an additional group of composites irradiated without aligners served as the control. The DC% measurements were performed using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The DC% across the aligners were (median values) 33.8%-44.8% for CLA, 33.6%-40.8% for INV, 32.8%-40.6% for GRP, and 40.0%-51.7% for the control group. The DC% values of the attachments cured under any aligner were significantly lower than that of the corresponding control, with the values recorded on the top surfaces being 6% higher than those on the bottom surfaces after adjusting for aligner group and composite type.

Coordination Adaptable Networks: Zirconium(IV) Carboxylates.

Vitrimers are 3D "covalent adaptable networks" (CANs) with flow properties thanks to thermally activated associative exchange reactions. This contribution introduces coordination adaptable networks, or CooANs, that are topologically related to metal-organic frameworks with octahedral Zr6 clusters as secondary building units in a carboxylic acid-functionalized acrylate-methacrylate copolymer matrix. A series of Zr-CooAN-x materials (x=percent of Zr6 loading relative to maximum capacity) was synthesized with x=5, 10, 15, 20, 25, 50 and 100. The mechanical and rheological investigations demonstrate vitrimer-like properties for x up to 50, the crosslink migration being ensured by carboxylate ligand exchange, with relaxation becoming slower as the Zr6 content is increased. The flow activation energy of Zr-CooAN-10 is 92.9±3.6 kJ mol-1 . Rapid (30 min) hot-press reshaping occurs at temperatures in the 50-100 °C range under a 3-ton pressure and does not significantly alter the material properties.

Formulation of non-effervescent floating matrix tablets of metronidazole using <I>Abelmoschus esculentus</I> gum as binder and 2-camphanone as sublimating agent.

The aim of this study was to formulate non-effervescent floating drug delivery system of metronidazole tablets using Abelmoschus esculentus (Okra) (AE) gum as a binder and 2-camphanone (camphor®) as the sublimating agent. Granules were prepared by wet granulation technique using varying concentrations of AE gum (2, 4, 6 and 8% w/w) admixed with 1%w/w acrylate methacrylate copolymer. A 30 %w/w of 2-camphanone was used as the sublimating agent. The granules were characterized for micromeritic properties. And thereafter, compressed at a compression pressure of 25 N/m2 using a Manesty single punch tableting machine. The metronidazole tablet was then sintered at 70oC for 12 h. Drug-excipient compatibility study was done using Fourier Transform Infra-red Spectroscopy (FTIR). Tablets were evaluated for floating lag time, in-vitro buoyancy and release kinetics. FTIR studies showed that the excipients and the active pharmaceutical ingredient (API) i.e. metronidazole, were compatible. All the granules were free flowing, with Carr’s index ≤ 15 %, Hausner ratio ≤ 1.18 and angle of repose of ≤ 33.5o. The tablets had hardness and friability values of 5.0-9.5 N and 0.4-0.8% respectively. The floating lag time was 0 s showing that the tablets floated immediately after immersion in the simulated gastric fluid. The maximum % release (m∞) and time to achieve it (t∞) were ≥ 88 % and ≥ 10 h, respectively. Release exponent (n) for all the formulations had values >0.45, hence their release was by non-Fickian diffusion. Non-effervescent floating matrix tablets of metronidazole were formulated using AE gum as the binder and 2-camphanone as the sublimating agent. The formulated floating tablets had increased in-vitro retention time, which indicated potential for sustained release of the drug. If well developed, this may help reduce the oral dosing frequency and encourage patient adherence to the drug therapy.
 Keywords: Non-effervescent, Abelmoschus esculentus, 2-camphanone, floating

Comparison of Microencapsulation by Emulsion-Solvent Extraction/Evaporation Technique Using Derivatives Cellulose and Acrylate-Methacrylate Copolymer as Carriers

Microencapsulation is a useful method to prolong a drug release from dosage forms and to reduce its adverse effect (1) among various available methods. The microencapsulation of hydrophilic active ingredients requires the use of a polar dispersing phase such as a mineral oil. Acetone/paraffin systems are conventionally used. The current study aimed to investigate two different microencapsulation techniques comparatively, water in oil in oil (w/o/o) and oil in oil (o/o), for theophylline (TH) loaded ethylcellulose (EC), cellulose acetate butyrate (CAB), Eudragit RS and RL microspheres with regard to loading efficiency, release and degradation kinetics. Microspheres were prepared by the emulsification method by solvent diffusion/evaporation technique and different polymers which were incorporated into microspheres to control the release rate of drug. Theophylline (TH) was chosen as a model drug. The emulsion technique was investigated for to prepare theophylline microparticles. EC and CAB and acrylatemethacrylate copolymer corresponding to the above ratios were selected as microparticles wall materials. The effects of type polymers on the physical characteristics and dissolution of the microparticles were also studied. However, the TH loading efficiency (for w/o/o emulsion about 90.64% and o/o emulsion about 73.90/5 to 95.90%) and the TH release kinetics were influenced by the microencapsulation technique. The results demonstrated that the o/o microspheres (containing of CAB) was most appropriate, providing a high encapsulation efficiency (95.90%) and low initial burst release (6.45%). The microspheres prepared with CAB polymer showed faster dissolution rate than other polymers with 0.75: 1 drug to polymer ratio. The double emulsion technique with EC as wall material gave the high dissolution efficiency (80.48%) of microcapsules. Eudragit RS microspheres showed higher yield (90%). The release of TH from CAB and Eudragit RL walled microcapsules was slow whilst the release from those of EC and Eudragit RS were faster. The type of polymer and the drug to polymer ratio were found to be the key factors affecting the release profile which could lead to microspheres with desired release behavior.

Comparison of Microencapsulation by Emulsion-Solvent Extraction/ Evaporation Technique Using Derivatives Cellulose and Acrylate-Methacrylate Copolymer as Carriers

Comparison of Microencapsulation by Emulsion-Solvent Extraction/ Evaporation Technique Using Derivatives Cellulose and Acrylate-Methacrylate Copolymer as Carriers

Preparation and in vivo evaluation of spray dried matrix type controlled-release microparticles of tamsulosin hydrochloride for orally disintegrating tablet

The objective of this study was to achieve an optimal formulation of spray dried matrix type controlled-release (MTCR) microparticles containing tamsulosin hydrochloride for orally disintegrating tablet. To control the release rate of tamsulosin hydrochloride, Acrylate-methacrylate copolymer (Eudragit® L-100 or Eudragit® S-100) and ethylcellulose were employed on the composition of MTCR microparticles. Physicochemical properties of MTCR microparticles such as particle size and SEM were characterized. Pharmacokinetic parameters of tamsulosin hydrochloride were evaluated in the rats after oral administration. MTCR microparticles were spherical microparticles of around 10 µm diameter with a corrugated surface. ODTs containing MTCR microparticles were disintegrated within 30 s and MTCR microparticles were able to control the release rate of tamsulosin hydrochloride following Fickian diffusion mechanism. The in vitro release rates of tamsulosin hydrochloride from MTCR microparticles were proportional to the ratio of Acrylate-methacrylate copolymer to ethylcellulose. Moreover, MTCR microparticles retarded the in vivo release rate of tamsulosin hydrochloride without reducing the bioavailability. Our results suggest that MTCR microparticles may be potential oral dosage forms to control the release and to improve the bioavailability of tamsulosin hydrochloride.

Thixotropic phenomenon in flocculated aqueous dispersions of acrylate methacrylate copolymers

Aqueous gels of two analogous, water-insoluble copolymers A and B have been formed by addition of excess water to concentrated ethanol solutions of the polymers. A and B differed only in their content of cationic groups in a ratio 2:1 (A:B). The gels were converted permanently to fluids (i.e. gel-sol transformation) at high shear rates. Stability of the resulting polymer dispersions depended on the presence and mutual repulsion of the polymer cations. Polymer B dispersions were less stable to the flocculating effect of an electrolyte (sodium chloride). At certain critical concentrations, 0.2 M NaCl (for polymer A), or 0.1 M NaCl (for polymer B) the electrolyte flocculated the otherwise stable dispersions to a gel structure. The electrolyte-flocculated gels were readily redispersed to fluids by shaking but reverted to gels on standing (thixotropic). In contrast the original coacervated gels (without electrolyte) could not be redispersed easily with manual shaking. Lower polymer-polymer interaction in the thixotropic system relates possibly to increases in particle size and irregularity of particle shape during flocculation.

Solute adsorption and concentration-dependent permeability in certain polymer films

Certain parameters (solute adsorption, permeability and swellability) of films of a cationic acrylatemethacrylate copolymer have been determined as functions of the solute (sulphacetamide sodium) concentrations. Both permeability coefficients and the free (unadsorbed fraction of solute increased almost proportionately during increase in solute concentration 1-5%, above 5%, further increase in the fraction of free solute was slight, while the permeability coefficients decreased slightly. The solute also reduced film swellability but the observed concentration-dependent permeability related more to the adsorption phenomenon.

Effect of polymer cation content on certain film properties.

Mixing of two acrylate-methacrylate copolymers designated A and B and differing only in cation (quaternary ammonium) content in the ratio 2:1 (A:B) provided a means of varying polymer cation content in resulting films. Film permeability to the permeant urea, increased with increase in cation content; a two phase change characterized by a slow increase at a low cation content level followed by about 13 times more rapid increase at high cation content level. The point of transition from the slow to the rapid phase was 53 moles cation per mole polymer chain. On average a fold increase in cation content resulted in a 500 fold increase in permeation rate. Increases in film swelling and pore size also accompanied the increase in cation content, but the change in permeability was more positively correlated with the corresponding change in film pore size. Mutual repulsion by charged groups during film formation is suggested as a factor promoting the formation of large pores in the film at high cation content.

Casting solvent effects on the permeability of polymer films of differing quaternary ammonium (cation) content.

Films of certain acrylate-methacrylate copolymers of varying cation (quaternary ammonium) content were cast from three different solvents: acetone, chloroform, and ethanol; their permeability to urea was determined at 30 degrees C. In films containing 66 mole cation mol-1 polymer chain, and cast from acetone, chloroform or ethanol, the permeation rates were 480,900 and 2807 mg h-1, respectively. Differences in permeation rates were however less significant when polymers of cation content lower than 46 mole cation mol-1 polymer chain were used to form films. This observation may relate to differences in the degree of dissociation of the polymer in the different solvents.

Permeability asymmetry in composite films of an acrylate-methacrylate copolymer [proceedings

Permeability asymmetry in composite films of an acrylate-methacrylate copolymer [proceedings

Matrix release from tablets prepared with aqueous dispersion of an acrylate methacrylate (a water – insoluble) copolymer as binder

PURPOSE: To investigate the binder effect of aqueous dispersions of acrylate methacrylates (AMA) copolymer with a view to obtaining matrix (non-disintegrating) tablets with a retard release property. METHODS: Aqueous dispersions of AMA (1-15% w/v) were formed by a coacervation procedure using ethanol (10 ml) as solvent and water (90 ml) as non-solvent for the copolymer. The aqueous dispersions were used to wet–mass the drug (paracetamol) powder. Resulting granules were compressed to 500 mg tablets using a single punch machine. The tablets were subjected to hardness, friability, disintegration and dissolution tests. RESULTS: The granules formed hard tablets (tensile strength 1 - 2.0 MNm-2) with low friability decreasing from 2 to 1 % as the AMA binder concentration increased from 0.75 to 11.25% w/w. The tablets failed to disintegrate in 3 hr. Drug release generally followed the Higuchi square root of time kinetic (R2
0.95). The AMA binder markedly retarded drug release as reflected by the sharp decrease in the dissolution rate constant from 30 min–2 (AMA, 0.75% w/w) to 9 min–2 (AMA, 11.25% w/w). CONCLUSION: The AMA dispersion is an effective binder, producing matrix tablets with a retard release property controlled by the binder content in the tablets. Keywords: Acrylate methacrylate copolymer; Aqueous dispersions; Matrix tablets, Retard release; Friability index; Tensile strength.

In Vitro Evaluation of Chemically Cross-Linked Shape-Memory Acrylate−Methacrylate Copolymer Networks as Ocular Implants

Acrylates have been used in ophthalmic practice as a paradigmatic implant material for decades, especially as intraocular lens for their excellent transparency. A novel polymeric shape memory system of chemically cross-linked acrylate-methacrylate copolymer networks was developed and characterized in this study. The thermomechanical properties, shape memory properties, transparency, and surface wettability as well as cytotoxicity were systematically evaluated to mimic the in vivo situation by differential scanning calorimetry (DSC), tensile tests, spectrophotometer, Abbe refractometer, contact angle measurements, and MTT assay. It was found that the chemically cross-linked copolymer network behaves as an elastomer capable of arbitrary shaping above the glass-transition temperature. Transition temperatures of the networks were tunable through the change of the composition of monomers.

Microstructure Analysis of Acrylate-Methacrylate Copolymers by 13C NMR Spectroscopy

The carbonyl signal in the 13C NMR spectra of copolymers of methyl methacrylate and several acrylates (methyl to butyl) has been investigated to obtain detailed information on distribution of sequences in the macromolecular chain up to configurational-compositional pentads. Complementary information on distribution of even sequences can be derived from the signal of β-CH2 carbons of the main chain. Incremental calculation of the chemical shifts of the individual sequences can be performed for both carbonyl and methylene signal and permit for spectral simulation and verification of the signal attribution to the respective sequences.

Polymeric microparticles prepared by supercritical antisolvent precipitation

This work has as main objective the development of a model process to obtain microparticles of an acrylate–methacrylate copolymer (Eudragit L100 ® and Eudragit EPO ®) using supercritical carbon dioxide (SC-CO 2) as antisolvent (GAS). After studying the behaviour of the copolymers in SC-CO 2 at different operation conditions (pressure, temperature and presence of ethanol (EtOH)), efforts were invested in the optimization of Eudragit EPO ® precipitation from an organic solution using carbon dioxide as antisolvent in batch mode. After loading the precipitation vessel with a fixed quantity of the copolymer dissolution, the SC-CO 2 has been added until the pressure of operation has been reached. Three process parameters, namely, solution nature, presence of surfactants and organic solvent removal step, have been evaluated. Microparticles with mean diameter from about 2 to 12 μm are obtained.

Effect of protective coating of aspirin tablets with acrylatemethacrylate copolymers on tablet disintegration times and dissolution rates

Tablets of aspirin (a moisture degradable drug) have been film coated with two analogous Eudragit RL and RS copolymers designated here as A and B which differ only in their cation content in the ratio 2:1 (A:B). A, is therefore more hydrophilic than B. The tablets were film coated with ethanol solutions of these two polymers. Film coating with either A or B significantly reduced the moisture uptake potentials of the tablets but caused an increase in the disintegration times of the tablets and retarded dissolution rates. The mean disintegration times were 0.5±0.1 min (uncoated tablets), 16±2.5 min (tablets coated with A) and 115±3.6 min (tablets coated with B). The corresponding dissolution rates % h -1 were 28.3 for uncoated, 16.6, coated with A and 14.8, coated with B, respectively. Thus, coating with polymer B considerably impaired the disintegration and dissolution properties of the tablets.

Effect of matrix granulation and wax coating on the dissolution rates of paracetamol granules

The study was carried out to investigate the release profile of matrix (non-disintegrating) granules consisting of paracetamol (drug) and acrylatemethacrylate copolymer, a matrix forming material. The effect of coating the matrix granules with wax on the drug release profiles was also investigated. The objective was to produce drug particles of different release profiles for application as multi-unit dosage forms. The matrix granules were formed by massing paracetamol powder with a concentrated ethanolic solution of the acrylatemethacrylate copolymer (40%, w/v) followed by drying and screening. Wax coating was achieved by mixing the matrix granules with a melt of carnuba wax. Conventional granules of paracetamol were made by granulation with starch mucilage (20%, w/v); this served as reference samples for comparison. The granules were subjected to size analysis, packing/flow property, friability and dissolution tests. All the granules (i.e. conventional, matrix as well as the coated matrix granules) flowed readily and were also compressible upon tapping. The compressibility index values were conventional granules (39±2.2%), matrix granules (27±1.8%) and coated matrix granules (24±1.9%). The friability values were conventional granules (1.96± ± ± ±0.02), matrix granules (0.78±

Influence of Methacrylic-Acrylic Copolymer Composition on Plasticiser-free Optode Films for pH Sensors

In this work we have examined the use of plasticiser-free polymeric films incorporating a proton selective chromoionophore for optical pH sensor. Four types of methacrylic-acrylic copolymers containing different compositions of n-butyl acrylate (nBA) and methyl methacrylate (MMA) were synthesised for use as optical sensor films. The copolymers were mixed with appropriate amounts of chromoionophore (ETH5294) and a lipophilic salt before spin coated on glass slides to form films for the evaluation of pH response using spectrophotometry. Co-polymer films with high nBA content gave good response and the response time depended on the film thickness. A preliminary evaluation of the optical films of high nBA content with pHs from 2 - 14 showed distinguishable responses from pH 5 - 9. However, the adhesion of the pH sensitive film was good for copolymers with higher content of MMA but not for films with high nBA.

Parameters to be Considered in the Simulation of Drug Release from Aspirin Crystals and their Microcapsules

Purpose: Drug microparticles may be microencapsulated with water-insoluble po lymers to obtain controlled release, which may be further determined by the pa rticle d istribution. The purpose o f t his s tudy was to de termine the drug release pa rameters needed for the theoretical prediction of the release profiles of single aspirin crystals and their microcapsules. Method: Four single crystals of aspirin of varied weight and orthorhombic in shape or their microcapsules also of varied weights were randomly selected for the study. The microcapsules were walled with an acrylatemethacrylate copolymer ( wall thickness, 11 i m). The following parameters were evaluated: the order of release, the dissolution rate constant, k (crystals), the diffusion coefficient, D (microcapsules), the maximum release m∞ and time to attain it t∞. These parameters were in turn used to simulate the release profiles of hypothetical single particles of a wide range size distribution, 0.3 ‐ 1.4 mm at 0.1mm intervals. Results: The e mpirical single crystals exhibited an initial zero o rder ( 93%; dissolution constant = 4.4 min -1 ) followed by a first order release (6%; dissolution constant = 0.38 min -1 ). Maximum release from each of the crystals was 99% of the initial particle weight; thus m∞ was a constant fraction of the initial particle weight. A zero order release consistent with a Fickian diffusion model was displayed b y the single microcapsules (diffusion coefficient, 5.4x10 -4 mm 2 min -1 ). At same particle weight the release parameters m∞, t∞, and the slopes of the rate order plots compared favourably with the theoretical data. Conclusion: The study indicates that the empirical release data on a few single particles can be used to predict the release profiles of single particles of a wide range of size distribution. This finding may be exploited in the prediction of drug release from polydisperse systems.

Preparation and characterization of drug-loaded polymethacrylate microspheres by an emulsion solvent evaporation method

Microspheres containing the anti-hypertension drug, felodipine, were prepared by the emulsion solvent evaporation method (o/o) using acrylate methacrylate copolymers, Eudragit RL PO and Eudragit RS PO, as wall materials. In order to increase the encapsulation efficiency, a mixed solvent system comprising 1:1 proportions of acetonitrile and dichloromethane was used as a dispersed phase. The morphology of the microspheres was evaluated using a scanning electron microscope, which showed a spherical shape with smooth surface. The mean sphere diameter was between 9.5-13.2 #119 m and the microencapsulation efficiencies ranged from 51.4-80.4%. The release profiles and encapsulation efficiencies depended strongly on the structure of the polymers used as wall materials. The release rate of the Eudragit RS PO microspheres was much lower than that of Eudragit RL PO microspheres. Whereas Eudragit RL PO microspheres followed the Higuchi rule, Eudragit RS PO microspheres exhibited a triphasic release profile. It is concluded that drug release rate can be controlled by choice of polymer type.