Removal of cationic dyes from aqueous solutions with poly (<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide-<Emphasis Type="Italic">co</Emphasis>-itaconic acid) hydrogels

In this study, N-isopropylacrylamide-based temperature and pH-sensitive hydrogels were synthesized by free radical polymerization for removal of cationic dyes from aqueous solutions. For this purpose, N-isopropylacrylamide was copolymerized with various amounts of sodium salt of itaconic acid in the presence of crosslinking agent (N,N-methylene bisacrylamide). The chemical structures of hydrogels were characterized by FT-IR analysis. In order to investigate swelling properties of the hydrogels, water absorption (swelling) and shrinking (deswelling) kinetics, the equilibrium swelling ratios in water and different pH buffer solutions, and the temperature dependent swelling ratios were determined. Then, their adsorption properties such as adsorption capacities, kinetics, isotherms were investigated in case of their usage in removal of Safranine T (ST), Brilliant Green (BG), and Brilliant Cresyl Blue (BCB) aqueous solutions. According to adsorbed dye amount, the adsorption capacities are followed the order BG > ST ≅ BCB. In addition, the results indicated that the pseudo-second-order kinetic model fitted better than the data obtained from pseudo-first-order model for the adsorption of all dyes onto hydrogels. Furthermore, according to effect of the initial dye concentration findings, it is concluded that, Freundlich isotherm explains the adsorption better than Langmuir isotherm.     

Synthesis and characterization of pH- and thermoresponsive Poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide-co-itaconic acid) hydrogels crosslinked with <Emphasis Type="Italic">N</Emphasis>-maleyl chitosan

Biodegradable cross-linker N-maleyl chitosan (N-MACH) was synthesized with chitosan (CS) and maleic anhydride (MA) by acylation. With N-MACH cross-linker, a series of cross-linked poly(N-isopropylacrylamide-co-itaconic acid) [P(NIPAAm-co-IA)] hydrogels were prepared, and their pH-and temperature-responsive behaviors, water contents, swelling/deswelling kinetics were investigated. By alternating the NIPAAm/IA weight ratios, hydrogels had the volume phase transition temperature (VPTT) changed from 33 to 38 °C, whereas cross-linking density did not affect the VPTT apparently. The water content of hydrogels was controlled by the monomer weight ratios of NIPAAm/IA, swelling media, and the cross-linking density. The results of the influence of pH value on the swelling behaviors showed that the minimum swelling ratios of the hydrogels appeared in neutral buffer solution, which was attributed to chemical composition of the hydrogels and the swelling media. In the swelling/deswelling kinetics, all the dried hydrogels exhibited fast swelling within 480 min and fast deswelling within 20 min, which was independent of the content of IA and cross-linker.     

Preparation and characterization of polyelectrolyte complex of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-trimethyl chitosan/gellan gum: evaluation for controlled release of ketoprofen

N,N,N-Trimethyl chitosan, a highly water soluble derivative of chitosan, has been made by reductive methylation of chitosan by a three-step process reported in literature. A novel polyelectrolyte complex of this derivative with gellan gum has been made by mixing the aqueous solutions of the two polymers. The complex was characterized by FTIR, TGA, DSC and SEM techniques. Maximum yield of the complex was obtained at pH 2.0 with a gellan gum:trimethylchitosan ratio of 3:1. The swelling study indicated pH responsiveness of the polyelectrolyte complex sample, with higher swelling under neutral or slightly basic conditions. In vitro studies on the release of the drug ketoprofen from the polyelectrolyte complex matrix were conducted in simulated gastric and intestinal fluids. The results indicated release of 85–90 % of the entrapped drug in the media of pH 6.8 and 7.4 and less than 7 % release in the medium of pH 1.2. The kinetic analysis indicated the drug release to be a first-order process. The mechanism of water transport and drug diffusion is shown to be of Fickian type. The results prove the suitability of the polyelectrolyte complex as a matrix material for delivery of drugs with short half life such as ketoprofen in the slow release mode.     

Synthesis and Properties of 1,1-bis{[3-(<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-Dimethylamino)propyl]amido}alkane-di-<Emphasis Type="Italic">N</Emphasis>-oxides

A homologous series of new surface-active 1,1-bis{[3-(N,N-dimethylamino)propyl]amido}alkane-di-N-oxides were synthesized in the reaction of an appropriate diethyl 2-alkylmalonate with N,N-dimethylamino-1,3-propanediamine followed by oxidation with aqueous hydrogen peroxide. The adsorption isotherms of their aqueous solutions were measured and evaluated to obtain adsorption parameters: critical micelle concentration (CMC), surface excess concentration (Γ_CMC), equilibrium surface tension at the CMC (γ_CMC), cross-sectional area of the adsorbed surfactant molecule (A _CMC), efficiency of surface adsorption (pC₂₀), standard free energies of adsorption (ΔG°_ads), and micellization (ΔG°_CMC). All investigated di-amidoamines and di-N-oxides were practically non-toxic to selected bacteria and yeasts. These compounds are readily biodegradable in the Closed Bottle Test inoculated with activated sludge. Surface and biological properties showed that this group of N-oxide-type compounds has high surface activity and fulfills requirements for environmental acceptance.

Preparation and properties of a novel thermosensitive <Emphasis Type="Italic">N</Emphasis>-trimethyl chitosan hydrogel

A novel injectable thermosensitive hydrogel system composed of N-trimethyl chitosan chloride (TMC) and β-glycerophosphate (β-GP), coded as TMC/β-GP, was designed. The morphology and rheological behavior of hydrogels were characterized by scanning electron microscopy and rheometer, respectively. Their swelling properties were carefully studied. The results revealed that the TMC/β-GP system was liquid with low viscosity at low temperature, which allowed it to be an ideal injectable material for biomedical applications. It was interesting that the system kept in liquid status for a long time near 4 °C and transformed rapidly to gel status within 1 min upon heating to 37 °C. The hydrogel could be dissolved at acid pH, while it absorbed water at neutral and basic conditions. The release of BSA from TMC/β-GP gels was slow at neutral pH. The TMC/β-GP hydrogel is a promising vehicle for the drug release, tissue repairing and regeneration.     

Synthesis,Characterization and Properties of <Emphasis Type="Italic">N</Emphasis>-Alkyl-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-di(2-hydroxyethyl) Amine Oxides

N‐Dodecyl‐N,N‐di(2‐hydroxyethyl) amine oxide (C₁₂DHEAO) and N‐stearyl‐N,N‐di(2‐hydroxyethyl) amine oxide (C₁₈DHEAO) were synthesized with N‐alkyl‐diethanolamine and hydrogen peroxide. Their chemical structures were confirmed using ¹H‐NMR spectra, mass spectral fragmentation and FTIR spectroscopic analysis. It was found that C₁₂DHEAO and C₁₈DHEAO reduced the surface tension of water to a minimum value of approximately 28.75 mN m^?1 at concentration of 2.48 × 10^?3 mol L^?1 and 32.45 mN m^?1 at concentration of 5.21 × 10^?5 mol L^?1, respectively. The minimum interfacial tension (IFT_min) and the dynamic interfacial tension (DIT) of oil–water system were measured. When C₁₈DHEAO concentration was in the range of 0.1–0.5%, the IFT_min between liquid paraffin and C₁₈DHEAO solutions all reached the ultra‐low interfacial tension. Furthermore, their foam properties were investigated by Ross‐Miles method, and the height of foam of C₁₂DHEAO was 183 mm. It was also found that they showed strong emulsifying power.     

Synthesis of <Emphasis Type="Italic">p</Emphasis><Emphasis Type="Bold">-</Emphasis> and <Emphasis Type="Italic">n</Emphasis>-type Gels Doped with Ionic Charge Carriers

In this study, we synthesized the new kinds of semiconducting polymeric gels having negative (n-type) and positive (p-type) counter ions as charge carriers. The polyacrylamide gel was doped with pyranine (8-hydroxypyrene-1,3,6-trisulfonic acid, trisodium salt), having \textSO₃ ^- {\text{SO}}_{3}^{ - } ions as side groups and Na⁺ as counter ions, so-called p-type semiconducting gel. The doping process was performed during the polymerization where the pyranine binds to the polymer strands over OH group chemically via radical addition. In a similar way, N-isopropylacrylamide (NIPA) gel was doped with methacrylamidopropyltrimethyl ammonium chloride (MAPTAC), having Cl⁻ as counter ions, so-called n-type semiconducting gel. Here MAPTAC was embedded by copolymerization within the polymer network (NIPA). These semiconducting gels can show different electrical properties by changing the concentration of the doping agents, swelling ratio etc. We have shown that the pn junction, formed by combining p-type and n-type gels together in close contact, rectifies the current similar to the conventional Si and Ge diodes.     

An Improved Method for Synthesis of <Emphasis Type="Italic">N</Emphasis>-stearoyl and <Emphasis Type="Italic">N</Emphasis>-palmitoylethanolamine

Certain N-acylethanolamines interact with cannabinoid receptors and have anorexic and neuroprotective effects. Traditional methods for the synthesis of N-acylethanolamines use fatty acid chlorides, fatty acid methyl esters, free fatty acids and triacylglycerols as acyl donors to react with ethanolamine. In the present study, we investigated the feasibility of using fatty acid vinyl esters as the acyl donor to synthesize N-stearoyl and N-palmitoylethanolamine. Theoretically, the use of fatty acid vinyl esters should lead to an irreversible reaction because the volatile acetaldehyde by-product is easily removed. Four reaction conditions, i.e. catalyst concentration, substrate ratio, temperature, and time were evaluated. The reaction performed at mild temperatures and with an excess amount of ethanolamine which acted as both reactant and solvent resulted in the formation of high purity N-stearoyl and N-palmitoylethanolamine. When 20 mmol ethanolamine was reacted with 1 mmol vinyl stearate at 80 °C for 1 h with 1% sodium methoxide as catalyst, N-stearoylethanolamine with 96% purity was obtained after the removal of excess ethanolamine without further purification, while N-palmitoylethanolamine with 98% purity was obtained by reacting with the same substrate ratio at 60 °C for 1.5 h with 3% catalyst. Complete conversion of vinyl stearate and palmitate was achieved.     

Molecular-hydrodynamic study of poly(<Emphasis Type="Italic">N</Emphasis>-methyl-<Emphasis Type="Italic">N</Emphasis>-vinylacetamide) macromolecules

High-velocity sedimentation, translational isothermal diffusion, and viscometry in H₂O and DMF are used to investigate the samples and fractions of poly(N-methyl-N-vinylacetamide) synthesized by free-radical polymerization and fractionated in a chloroform-diethyl ether system. Molecular masses M and the Mark-Kuhn-Houwink-Sakurada relations are obtained for the fractions in the molecular mass range M × 10⁻³ = 3.5−540.0. The negative temperature coefficient of intrinsic viscosity is revealed for both solvents. The length of the Kuhn statistical segment and the hydrodynamic diameter of poly(N-methyl-N-vinylacetamide) macromolecules are estimated; the hydrodynamic volumes occupied by water-soluble poly(N-methyl-N-vinylacetamide), poly(1-vinyl-2-pyrrolidone), poly(vinylformamide), and pullulan molecules are compared.     

Synthesis and properties of silk sericin-<Emphasis Type="Italic">g</Emphasis>-poly(acrylic acid-co-acrylamide) superabsorbent hydrogel

A novel superabsorbent hydrogel has been synthesized with the crosslinking graft copolymerization of acrylic acid (AA) and acrylamide onto the chain of silk sericin. Potassium persulfate (KPS)–sodium sulfite (NaHSO₃) as redox initiation system and N,N′-methylenebisacrylamide (MBA) as crosslinker were used. The structure of the product characterized by Fourier transform infrared absorption spectroscopy and the surface morphology of the hydrogel were observed by scanning electron microscopy. The certain parameters of the graft copolymerization including the monomer, the initiator, the crosslinker concentration, neutralization degree of AA, reaction temperature, and time were systematically optimized to achieve a hydrogel with maximum swelling capacity (2150 g/g). The optimal conditions were initiator 8 mmol/L, MBA 2.5 mmol/L, neutralization degree of AA 75%, reaction temperature 55 °C, and time 6 h. The swelling ratio in salt solutions was also determined (in 0.9% NaCl aqueous solution: 98 g/g). In addition, the swelling capability of the hydrogel was measured in solutions with pH ranged from 1 to 13. The synthesized hydrogel exhibited a pH-dependent character. Water absorbency of the product in aqueous chloride salt solutions has the Na⁺ > Ca²⁺ > Mg²⁺ > Al³⁺ order in the investigated concentration.     

Adsorption of Bovine Serum Albumine Onto Poly (<Emphasis Type="Italic">N</Emphasis>-<Emphasis Type="Italic">t</Emphasis>-Butylacrylamide-co-Acrylamide/Maleic Acid) Hydrogels

In the present study, a series of ionic poly(N-t-butylacrylamide-co-acrylamide) [P(NTBA-co-AAm)] hydrogels were synthesized by free-radical crosslinking copolymerization of N-t-butylacrylamide (NTBA) and acrylamide (AAm) monomers in fixed amount, but changing amount of maleic acid (MA) comonomer in methanol using N,N-methylene-bis-acrylamide (BAAm) as the crosslinker, ammonium persulfate (APS) as the initiator, and N,N,N′,N′-tetramethylethylenediamine (TEMED) as the activator. The swelling behavior of these hydrogels was analyzed in buffer solutions at various pHs. The prepared hydrogels also were investigated swelling-deswelling transition in water depending on the temperature. For the bovine serum albumin (BSA) adsorption, the effect of pH, temperature, initial protein concentration and adsorption rate were investigated. Maximum BSA adsorption was observed at pH 5.0 which is close to the isoelectric pH of BSA (pH 4.8). The highest adsorption rate was achieved in about 12 h. and also, maximum BSA adsorption was found at +5°C.     

Ferrocenyl Monomers and Polymers of <Emphasis Type="Italic">N</Emphasis>-Allyl and <Emphasis Type="Italic">N</Emphasis>-Acrylatenaphthalimides

A series of N-allyl, N-ethylmethacrylate and N-phenylmethacrylatenaphthalimide monomers have been prepared with –C=CFc, –C≡CFc and –C≡CSiMe₃ substituents at the 4-position of the naphthalimide ring. All have been characterised by elemental analysis and spectroscopy; the X-ray structure of N-allyl-4-ethenylferrocenylnapththalimide is also reported. Free-radical polymerisation of these monomers gave homopolymers, random co- and terpolymers with polydispersities ranging from 1.7 to 3.2. Incorporation into a polymer matrix has no effect on the spectroscopic and electrochemical properties of the naphthalimide or ferrocenyl components. The ferrocenyl polymers are electrochromic and when oxidised give naphthalimide charge-transfer bands in the NIR; this electrochromism was examined by OTTLE techniques.     

<Emphasis Type="Italic">N</Emphasis>-Acylated Bacteriohopanehexol-Mannosamides from the Thermophilic Bacterium <Emphasis Type="Italic">Alicyclobacillus acidoterrestris</Emphasis>

Identification of molecular species of various N-acylated bacteriohopanehexol-mannosamides from the thermophilic bacterium Alicyclobacillus acidoterrestris by semipreparative HPLC and by RP-HPLC with ESI is described. We used triple-quadrupole type mass spectrometer, ¹H and ¹³C NMR for analyzing this complex lipid. CD spectra of two compounds (model compound—7-deoxy-d-glycero-d-allo-heptitol obtained by stereospecific synthesis, and an isolated derivative of hopane) were also measured and the absolute configuration of both compounds was determined. On the basis of all the above methods, we identified the full structure of a new class of bacteriohopanes, represented by various N-acylated bacteriohopanehexol-mannosamides.     

Study of the kinetics of oxidation of amines by potassium ferricyanide in the presence of <Emphasis Type="Italic">N,N</Emphasis>-dimethyldodecylamine <Emphasis Type="Italic">N</Emphasis>-oxide

This research reports on the oxidation of different amines such as dibutylamine, diethylamine, dipropylamine, ethylamine, ethylmethylamine, propylamine, triethylamine, and trimethylamine by 0.001 M potassium ferricyanide in the presence of 0.03 M NaOH at 25°C in aqueous medium and/or in 0.03 M N,N-dimethyldodecylamine N-oxide (DDAO). Oxidation rates were studied with a spectrophotometer at 420 nm. The experimental data showed that the reaction was first-order with respect to [amine] _T and [Fe(CN)₆]³⁻. Also, the rate constant (k _obs) had values within the concentration range of 0.015–0.05 M of NaOH and increased above the critical micelle concentration values of DDAO. The dependence of the reaction rate on the nature of the salt was also investigated, and the thermodynamic parameters ΔG ^*, ΔH ^*, and ΔS ^* were calculated. A pseudo-phase model was applied to the system, and the binding constant of the amine to DDAO micelles was calculated.     

Synthesis,characterization and antibacterial activity of quaternized <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">O</Emphasis>-(2-carboxyethyl) chitosan

N,O-(2-carboxyethyl)chitosan (N,O-2-CEC) was prepared from chitosan with 3-chloropropionic acid as modifying agent and NaOH as catalyst. Different quaternary ammonium groups were introduced into N,O-2-CEC by the reaction between N,O-2-CEC and different 2,3-epoxypropyl trialkyl ammonium chlorides in the presence of 25% NaOH aqueous solution, and obtained different quaternized N,O-2-carboxyethyl chitosans (QCECs). Structures of QCECs were characterized by FT-IR, ¹HNMR and gel permeation chromatography (GPC). Antimicrobial activity of QCECs was evaluated against a gram-negative bacterium Escherichia coli and a gram-positive bacterium Staphylococcus aureus. Compared with N,O-2-CEC and quaternized chitosans, the QCECs had much stronger antimicrobial activity, which increased with increasing chain length of the alkyl in the quaternary ammonium groups. The presence of benzyl in quaternary ammonium groups could endow QCECs with much better antimicrobial activity.     

Rapid pH‐dependent phase transition and elasticity of stimuli‐responsive cationic poly(N,N‐dimethylaminoethyl methacrylate) hydrogels prepared with a dimethacrylate crosslinker

Stimuli‐responsive hydrogels prepared from poly(N,N‐dimethylaminoethyl methacrylate) (PDMAEMA) and its copolymers have attracted much interest to serve in biomedical and pharmaceutical applications. To investigate pH‐dependent swelling and elasticity, a series of cationic hydrogels based on N,N‐dimethylaminoethyl methacrylate were prepared by free radical crosslinking copolymerization at 60 °C in the presence of tetraethylene glycol dimethacrylate as the crosslinker. The equilibrium swelling and the mechanical properties of the PDMAEMA hydrogels were investigated as a function of the gel preparation concentration. To explain the effect of pH on the equilibrium swelling of the hydrogels, pH‐dependent swelling studies were carried out in solutions of pH ranging from 2.1 to 10.7. It was found that the PDMAEMA hydrogels exhibit a rapid pH‐dependent phase transition in aqueous solutions; that is, the gels first remain in the swollen state at acidic pH then collapse in a very narrow range of pH. The results showed that the volume of PDMAEMA hydrogels in acidic conditions is about 10‐ to 40‐fold larger than that in the basic pH region. By using the Flory–Rehner theory, the characteristic network parameters of the PDMAEMA hydrogels were calculated and good agreement obtained between the swelling equilibria of hydrogels and their mechanical properties over the whole range of gel preparation concentration. © 2012 Society of Chemical Industry     

Swelling and mechanical behavior of charged poly(<Emphasis Type="Italic">N</Emphasis>-isopropylmethacrylamide) and poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide) networks in water/ethanol mixtures. Cononsolvency effect

Summary Swelling and mechanical behavior of negatively (ionic comonomer-sodium methacrylate) and positively (ionic comonomer-(2-acrylamidoethyl)trimethyl ammonium chloride) charged networks of poly(N-isopropylmethacrylamide) (PIPMAm) and poly(N-isopropylacrylamide) (PIPAAm) was investigated in water/ethanol mixtures at room temperature. Strong cononsolvency effect was observed for uncharged and negatively charged gels of both systems; while for neat solvents high degree of swelling Q was observed, for solvent mixtures pronounced minima in swelling were found. Swelling minima are connected with the coil-to-globule transition of network chains and their characteristic parameters-concentration of ethanol at the minimum, c_eth,m, and corresponding swelling degree, Q_m, were determined. With increasing amount of negatively charged ionic comonomer the minimum in swelling shifts to higher c_eth,m values and Q_m increase. On the other hand, positively charged networks of both systems exhibit roughly constant Q values practically independent of solvent mixtures compositions. For all four systems it was found that mechanical behavior is predominantly determined by the degree of swelling regardless of charge concentration.     

Aqueous radical polymerization of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylacrylamide redox-initiated by aerobically catalytic oxidation of water-soluble tertiary amines

Catalytic oxidation of water-soluble tertiary amines by complexes of Cu^II, Fe^III and Co^II was utilized to initiate radical polymerization of N,N-dimethylacrylamide (DMAAm) in aqueous solution at 70–80 °C. The oxidation of tertiary amines by Cu^II was studied by proton nuclear magnetic resonance spectroscopy and online ultraviolet–visible spectrophotometry. The polymerization kinetics was monitored by gas chromatography, and molecular weight of the PDMAAm was measured by gel-permeation chromatography coupled with multi-angle laser light scattering. Oxidation of tertiary amines occurs predominantly via formation of C_alpha·radicals to initiate polymerization of electron-deficient monomers and N-dealkylation, and redox equilibrium between Cu^I/L and Cu^II/L is established at a faster rate in aqueous media. Fe^III and Cu^II complexes are efficient catalysts as each catalyst molecule could generate above 10 propagating radicals in 5 h, while Co^II complex might involve in oxidation of tertiary amines in non-radical pathway, leading to a low catalytic efficiency. Water-soluble tertiary amines such as N,N-dialkylethanolamine (alkyl = methyl, ethyl etc.) are reducing agents of a higher activity in aqueous media than those primary or secondary analogues. Our strategy renders it possible to prepare polymer of alpha-amino functionality via one-pot process from commercially available commodity reagents under practical conditions with negligible catalyst residue.     

Solubility of Two Disperse Dyes Derived from <Emphasis Type="Italic">N</Emphasis>-Alkyl and <Emphasis Type="Italic">N</Emphasis>-Carboxylic Acid Naphthalimides in the Presence of Gemini Cationic Surfactants

The solubility of naphthalimide-based monoazo dyes containing N-ethyl and N-ethanoic acid groups was investigated in the presence of a conventional monomeric counterpart (DTAB) and two cationic gemini surfactants (12-4-12 or 14-4-14) individually. The effective parameters on dye solubility such as temperature, time and concentration of surfactants were investigated by UV–Visible spectrophotometry. The results demonstrate that the solubility of both dyes was considerably increased at concentrations above the surfactant CMC. The wavelength for the maximum absorbance of dyes in the aqueous solution shifts toward longer wavelengths with changes in the concentration of the cationic surfactants. A kinetic study of solubilization of dyes in cationic surfactants solution showed that the rate of solubilization follows the pseudo-first-order reactions. Rates of solubilization were in the range of 0.5 × 10⁻³ to 6.8 × 10⁻³ min⁻¹ for both dyes. The disperse dye containing a carboxylic acid group (dye 2) has a higher solubility rate than the dye containing an alkyl group (dye 1). The type of surfactant has a very low effect on adsorption of dye 1 onto the polyester fibers, whereas changing the surfactant type from DTAB to 12-4-12 or 14-4-14 causes adsorption of dye 2 on polyester to decrease.     

Synthesis,characterization, and drug release properties of macroporous dual stimuli responsive stereo regular nanocomposites gels of poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide) and graphene oxide

Nanocomposite stereoregular hybrid gels of poly(N-isopropylacrylamide) were prepared in 1:1 methanol–water mixture in the presence rare earth yttrium trifluoromethanesulfonate Lewis acid and graphene oxide (GO). The nanocomposite gels were characterized by swelling ratio measurements at different temperatures and different pH, deswelling kinetics, scanning electrone microscopy, FTIR, thermogravimetric analysis, powder XRD, Raman spectroscopy, LCST measurement by DSC etc. Drug release experiments also done by using tramadol hydrochloride as a model drug to check their suitability in application. All results were explained on the basis of porosity, cononsolvency of the synthesis solvents, hydrophilicity, isotacticity, pH effect, interactions between solvents and polymer molecules, interactions between polymer and GO or interactions between GO and solvents etc.