Cope elimination and complexation of poly(dimethylaminoethyl methacrylate N-oxide)

Poly(dimethylaminoethyl methacrylate N-oxide) (poly(DMAEMNO)) was prepared by oxidation of poly(dimethylaminoethyl methacrylate) with hydrogen peroxide in methanol. From thermogravimetric and IR spectroscopic investigations Cope elimination of amine oxide group in poly(DMAENO) was found to occur at 120–150°C. The postpolymerization of partially pyrolyzed polymer carrying vinyl ester group as pendant was performed with azobisisobutyronitrile at 60°C in methanol to give cross-linked polymer that was found to form hydrogel. Poly(DMAEMNO) gave metal–polymer complexes with CuCl₂, ZnCl₂, and CoCl₂. Cobalt–polymer complex had a constitution of 1:2 of metal ion to amine oxide group, while copper– and zinc–polymer complexes seemed to have structures of 1:1 and 1:2 of metal ion to amine oxide group. Furthermore, polymer complexes of poly(DMAEMNO) with poly(methacrylic acid) and poly(acrylic acid) were found to be formed by mixing aqueous solutions of both polymers and also by radical polymerization of the acid monomers in the presence of poly(DMAEMNO). From elemental analysis, thermogravimetric investigation, and measurement of turbidity it was concluded that the resulting polymer–polymer complexes contained more than one acid monomer unit per one N-oxide unit.     

Chain microstructure and conformation of partially quaternized poly(dimethylaminoethyl methacrylate)

¹H-NMR spectroscopy was used to establish the chain microstructure and conformation produced by the quaternization reaction of syndiotactic poly[2-(dimethylamino)ethyl methacrylate], a polymer with tertiary amino groups in the side chains. A chain microstructure with mini blocks of modified units was found by analyzing the N⁺CH₃ signal that was proved to be split in accordance with the composition triads. The macromolecular backbone changes its form by quaternization, from a close to an expanded coil, was confirmed by light scattering measurements and NOE spectra modifications. The two linked processes, the block formation and chain expansion can be the key in developing a reaction mechanism explaining both positive and negative deviations from a second-order kinetic model.     

Biodegradable and biomimetic poly(epsilon-caprolactone)/poly(lactobionamidoethyl methacrylate) biohybrids: synthesis, lactose-installed nanoparticles and recognition properties

Biodegradable and biomimetic SPCL-PLAMA biohybrids were synthesized via ATRP and characterized by FT-IR, (1)H NMR, GPC and DSC. Biohybrids with small PDI were obtained, and the block length of the PLAMA glycopolymer could be varied linearly by the varying the molar ratio of glycomonomer to macroinitiator. The outer PLAMA glycopolymer restrained the crystallization of inner PCL segments. The self-assembly properties of amphiphilic biohybrids were studied. Lactose-installed aggregates were fabricated in aqueous solution; they changed from spherical micelles to vesicles with increasing weight fraction of hydrophobic PCL. The SPCL-PLAMA biohybrids showed specific recognition for RCA(120) lectin.     

Synthesis and characterization of stimuli‐sensitive micro‐ and nanohydrogels based on photocrosslinkable poly(dimethylaminoethyl methacrylate)

The aim of this work was the development of a versatile route for the preparation of temperature‐ and pH‐responsive hydrogels with small dimensions. The copolymerization of N,N‐dimethylaminoethyl methacrylate with various amounts (5 and 10 mol %) of dimethylmaleimidoethyl methacrylate in solution with 2,2′‐azobisisobutyronitrile as an initiator is described. The structural and molecular characterization of the copolymers was performed with proton nuclear magnetic resonance, Fourier transform infrared, and ultraviolet spectroscopy, as well as size exclusion chromatography. Differential scanning calorimetry and thermogravimetry were used for the thermal characterization of the copolymers. Micro‐ and nanohydrogels of the copolymers were prepared by photocrosslinking. The gels obtained by photocrosslinking were characterized with a combination of surface plasmon resonance and optical waveguide spectroscopy, dynamic light scattering, and scanning electron microscopy. The hydrogels showed temperature‐ and pH‐responsive behavior. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 669–679, 2007     

Synthesis and curing of poly(glycidyl methacrylate) nanoparticles

Glycidyl‐functional polymer nanoparticles [poly(glycidyl methacrylate) (PGMA)] were fabricated with microemulsion polymerization. The successful fabrication of PGMA nanoparticles was confirmed by Fourier transform infrared spectroscopy and transmission electron microscopy (TEM). A TEM image showed that the average diameter of the PGMA nanoparticles was approximately 10–28 nm and was fairly monodisperse. As the surfactant concentration increased, the average size of the nanoparticles decreased and approached an asymptotic value. A significant reduction of the nanoparticle size to the nanometer scale led to an enhanced number of surface functionalities, which played an important role in the curing reaction. The PGMA nanoparticles were cured with a low‐temperature curing agent, diethylene triamine, to produce ultrafine thermoset nanoparticles. The low‐temperature curing process was performed below the glass‐transition temperature of PGMA to prevent the coagulation and deformation of the nanoparticles. A TEM image indicated that the cured PGMA nanoparticles did not exhibit interparticle aggregation and morphological transformation during curing. The average size of the cured PGMA nanoparticles was consistent with that of the pristine PGMA nanoparticles © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2258–2265, 2005     

Synthesis of linear and starlike polymers from poly(propylene glycol) methacrylate using controlled radical polymerization

The copper‐catalyzed atom transfer radical polymerization (ATRP) of poly(propylene glycol) methacrylate (PPGM) in solution to produce linear and starlike polymers is reported, using methylethyl ketone as the solvent and a temperature of 80 °C. The ATRP system used was efficient for polymerization of the functionalized monomer without protecting hydroxyl end groups of monomer. The polymerizations were consistent with “living” or controlled processes, as revealed by the linear evolution of molecular weight with conversion. Increasing the [M]₀:[I]₀ ratio resulted in increasing molecular weights, whereas the polydispersity indices remained low (M_w/M_n < 1.4) even at high conversion. Decreasing the [CuBr]₀:[I]₀ ratio resulted in lower conversions, slightly larger polydispersities, and decreased molecular weights, likely resulting from a lower initiation efficiency. Polymers were characterized by ¹H and ¹³C NMR; molecular weights of polymers with low degrees of polymerization were estimated by end‐group analysis from ¹³C NMR spectra obtained using distortionless enhancement by polarization transfer and the gated decoupling techniques. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 334–343, 2002     

Thermally responsive polymeric micellar nanoparticles self-assembled from cholesteryl end-capped random poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide): synthesis, temperature-sensitivity, and morphologies

Cholesteryl end-capped thermally responsive amphiphilic polymers with two different hydrophobic/hydrophilic chain-length ratios were synthesized from the hydroxyl-terminated random poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) and cholesteryl chloroformate. The hydroxyl-terminated precursor polymers with narrow molecular weight distributions were synthesized by free-radical polymerization using 2-hydroxyethanethiol as a chain-transfer agent. The aqueous solutions of the cholesteryl end-capped copolymers exhibited reversible phase transitions at temperatures slightly above human body temperature, with the lower critical solution temperature values being 37.7 and 38.2 degrees C, respectively. The critical micelle concentration values of the two cholesteryl end-capped polymers were 9 and 25 mg/L, respectively. Polymeric micellar nanoparticles were prepared from the amphiphilic polymers using a dialysis method as well as a direct dissolution method. Transmission electron microscope studies showed that the micellar nanoparticles existed in different morphologies, including spherical, star-like, and cuboid shapes. Pyrene as a model hydrophobic compound could be readily encapsulated in these polymeric nanoparticles, at loading levels of 1.0 and 0.8 mg/g for the two cholesteryl end-capped polymers, respectively. The temperature sensitivity and unusual morphology of these novel polymeric nanoparticles would make an interesting drug delivery system.     

Amphiphilic poly(ethylene glycol)-b-poly(ethylene brassylate) copolymers: One-pot synthesis,self-assembly,and controlled drug release

A set of amphiphilic poly(ethylene glycol)-b-poly(ethylene brassylate) (PEG-b-PEB) copolymers based on the PEB hydrophobic block was first synthesized by ring-opening polymerization of ethylene brassylate with an organic catalyst. The EB/PEGmolar ratios and reaction times were adjusted to achieve different chain lengths of PEB. Block copolymers that were characterized by ¹H NMR and GPC could selfassemble into multimorphological aggregates in aqueous solution, which were characterized by DLS and TEM. The hydrophobic doxorubicin (DOX) was chosen as a drug model and successfully encapsulated into the nanoparticles. The release kinetics of DOX were investigated.     

Dicyclopentadienyl complexes of titanium,niobium, and tungsten in the controlled synthesis of poly(methyl methacrylate)

Organometallic compounds Cp₂TiCl₂, (EtC₅H₄)₂NbCl₂, and (PrⁱC₅H₄)₂WCl₂ were assessed as additives that control polymer chain growth in the polymerization of methyl methacrylate. In the presence of compounds mentioned in amounts comparable with that of the initiator, a uniform process with no gel-effect occured and respective linear increase in the molecular weight of the polymer up to high degrees of the monomer conversion was observed.     

Effect of amines on the controlled synthesis of poly(methyl methacrylate) catalyzed by ruthenacarboranes

The effects of amines on the activity of ruthenium catalysts in the controlled synthesis of poly(methyl methacrylate) are reported at 80°C. The introduction of tert-butylamine or triethylamine into the polymerization system raises the polymerization rate by 1–2 orders of magnitude without reducing the high degree of control over the chain propagation step. The “living” character of methyl methacrylate polymerization in the presence of ruthenacarboranes and amines is proved by the fact that, as the monomer conversion increases, the molecular weight of the resulting polymer increases linearly and the polydispersity index decreases. The polymer can serve as a macroinitiator for postpolymerization and block copolymer synthesis.     

Solution behavior of progressively quaternized poly(dimethylaminoethyl methacrylate) as a function of charge density

Hydrodynamic behavior of progressively quaternized poly(dimethylaminoethyl methacrylate) (PDMAEM) in dilute and semi-dilute salt–free aqueous solutions as a function of molar mass and charge density, which varied from 5 up to 100 mol%, was studied. The role of long range electrostatic interactions on the viscosity and on the position and value of the reduced viscosity corresponding to the peak, η_red,p, as a function of the charge density of polycation has been evaluated. The overlap concentration of polyelectrolytes, c^∗, has been evaluated as the inverse of the intrinsic viscosity determined by fitting the viscometric results on Rao equation. The values of c^∗ have been discussed as a function of polyion molar mass and charge density. The c^∗ values calculated in the frame of Odijk model for polyelectrolytes having quaternization degree ?50 were lower but comparable with those determined by viscometry, for the same molar mass.     

Electrochemically controlled release based on nanoporous conducting polymers

An electrochemically controlled drug release system based on nanoporous polypyrrole (PPy) films was developed. Pyrrole and a model drug, fluorescein, were electrochemically copolymerized on glassy carbon (GC) electrodes modified with self-assembled multilayer polystyrene (PS) nanobeads, and PPy films incorporated with fluorescein as dopants were formed among the interstitial spaces of the tightly packed PS nanobead template. After the removal of the PS hard template, nanoporous PPy films incorporated with the drug fluorescein were obtained. Due to the porous morphology and huge surface area, the efficiency of the prepared PPy films in electrochemically releasing incorporated fluorescein was about nine times higher than that of conventional PPy films.     

Dendritic polymers based on poly(ethylene glycol) -co- poly(glycolic acid) -co- methacrylate and 2.0 G -polyamidoamine- metharylamide: Design, characterization, and in vitro degradation, and drug release properties

In this paper, the properties of the complete degradation process of newly synthesized multi-block 2.0 G-polyamidoamine-double bond (PAMAM-DB) and resoluble poly (ethylene glycol) -co- poly (glycolic acid) -co- methacryloyl chloride (PEG-co-PGA-co-DB, 4KG5-DB) macromonomers were reported. Rectangular shaped samples were prepared by crosslinking the components using both chemical and photo initiators and exposure to UV light. The aims of the study were to examine the effects of the vitro degradation and drug delivery of the crosslinking group on the properties of photocrosslinked hydrogels. The experimental variable was PAMAM-DB: 4KG5-DB ratio. The effects of this variable on local PH, water uptake, mass loss, and drug release were explored. Polymers were characterized by ¹H NMR, ¹³C NMR, FT-IR, and SEM. Our study revealed that polymers with 40%, 50%, 60% 4KG5-DB (mass fraction) showed more excellent mechanical properties, 40% also showed outstanding vitro degradation properties. In vitro drug release, however, 60% drug released mechanism seemed to approach the Fickian diffusion and possessed more excellent drug release properties compared with formulation 40% and 50%. In general, an increase ratio of 4KG5-DB led to a higher density of tree-like polymer which resulted in slower of degradation and drug release. Incorporation of 4KG5-DB into the polymer was critical for maintaining integrity and increasing hydrophilicity during degradation. These results obtained suggest that this system could be potential as a material for bone replacement and controlled delivery of drugs.     

Large core-shell poly(methyl methacrylate) colloidal clusters: synthesis, characterization, and tracking

We present a multistep procedure yielding large (diameter > 2 μm) monodisperse, fluorescently labeled core-shell poly(methyl methacrylate) (PMMA) latex particles via dispersion polymerization. The particles' physical properties were controlled by adjusting two reaction parameters, the initiator and chain transfer agent concentrations, which influence the molecular weight of the PMMA. Under certain conditions, particles with the requisite properties for fabricating colloidal clusters were synthesized. The resulting clusters represent a new type of nonspherical colloid that can be dispersed in a density- and refractive index-matching solvent, making them ideal for quantitative studies using confocal microscopy. To demonstrate the utility of our clusters, we measured the translational and rotational diffusion coefficients of a tetrahedral cluster by tracking the motion of its constituent particles in three-dimensional space. More broadly, our findings provide new insights concerning PMMA dispersion polymerization in apolar media.     

Radiation synthesis of poly[(dimethylaminoethyl methacrylate)-co-(ethyleneglycol dimethacrylate)] hydrogels and its application as a carrier for anticancer delivery

The use of hydrogels as carriers for anticancer delivery has been a subject of significant recent research. In our recent work, we have shown that diffusion-controlled delivery of flutamide from hydrogels containing poly (dimethylaminoethyl methacrylate (DMAEMA)/ethyleneglycol dimethacrylate (EGDMA)) can be possible and controlled by the three-dimensional structure. Hydrogels based essentially on dimethylaminoethyl methacrylate and different ratios of ethyleneglycol dimethacrylate monomers were synthesized using gamma radiation copolymerization. The influence of copolymer composition and pH value of the surrounding medium on swelling behavior into the glassy polymer were discussed. The results showed that the ratio of EGDMA in the comonomer feeding solution has a great effect on the gel fraction and water content in the final hydrogel. In this regard, it was observed that the increase of EGDMA ratio decreased these properties. The ability of the prepared copolymer to be used as drug carrier for anticancer drug-delivery system was estimated using flutamide as a model drug. In vitro drug-release studies in different buffer solutions show that the basic parameters affecting the drug release behavior of hydrogel are the pH of the solution and DMAEMA content of hydrogel.     

Solution properties of dendronized poly(hydroxy ethyl methacrylate) polymers

Four generations of dendronized polymers with a methacrylate backbone and hydroxy‐functionalized aliphatic polyester dendrons based on 2,2‐bis(methylol)propionic acid were studied in solutions by rheological measurements, dynamic light scattering, turbidimetry, and ¹H NMR self‐diffusion measurements to reveal the effect of increasing hydrophilicity and molecular size on their solution properties. The studied polymers were interesting new amphiphiles with a hydrophobic main chain and a hydrophilic shell. Evidence of aggregation upon the heating of the first‐generation polymer in an aqueous solution was obtained by dynamic light scattering and turbidimetry, reflecting the effect of the hydrophobic polymer backbone, whereas the higher generation polymers did not show aggregation upon heating. Although the dimensions of the polymers were observed to increase with increasing generation, all the polymers exhibited low viscosities and Newtonian flow behavior in both aqueous and dimethyl sulfoxide solutions. The relative viscosities of the polymers in water and dimethyl sulfoxide showed that the conformation of the polymers was somewhat more open in dimethyl sulfoxide, and this led to higher viscosities than those in water, in agreement with the ¹H NMR diffusion measurements, by which the dimensions were found to be larger for the polymers dissolved in dimethyl sulfoxide. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3674–3683, 2006