Micellization and applications of narrow-distribution poly[2-(dimethylamino)ethyl methacrylate]

Oxyanion-initiated polymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA), initiated by potassium benzyl alcoholate (BzOK), produced a number of well-defined, water-soluble benzyloxy end-capped homopolymers of various molecular weights. The structure of these homopolymers was confirmed by FTIR and ¹H NMR. The molecular weights of the polymers were estimated by comparing the ¹H NMR peak integrals for phenyl protons of the benzyloxy group with those of the dimethylamino protons of the monomeric unit. GPC analysis showed that these homopolymers possess a narrow molecular weight distribution ( ) in the range of 1.15–1.28. Under acidic or neutral conditions, the polymers exhibit the behavior of polymeric surfactants bearing protonized tertiary amines in their pendants, with critical micelle concentration (CMC) between 0.5 to 1 g/L and surface tension dropping below 40 mN/m. It was also found that the lower critical solution temperature (LCST) of the polymeric surfactants (as determined by UV-visible spectroscopy) varied with properties such as molecular weight, concentration, and pH in aqueous media. The polymeric surfactants showed excellent pH-response and emulsifier properties when used in the emulsion polymerization of styrene.     

Superhelices of poly[2-(acetoacetoxy)ethyl methacrylate

Poly[2-(acetoacetoxy)ethyl methacrylate] (PAEMA) homopolymers were found to self-assemble into hierarchical superstructures, that is, double-stranded helical tubes of either screw sense (scanning force microscopy). Both the diameter and the pitch of the superhelices are approximately 12 nm, and their length is 200-500 nm. It is proposed that PAEMA chains first organize into ribbons, the width of which determines the pitch of the helix, and then coil up into the helical superstructure. The formation of these structures is driven by the establishment of hydrogen-bridging interactions between adjacent acetoacetoxy groups (NMR and dielectric relaxation spectroscopy) and compensation of dipole moments.     

Target grafting of poly(2-(dimethylamino)ethyl methacrylate) to biodegradable block copolymers

A series of copolymers composed of methoxy poly(ethylene glycol) and a hydrophobic block of poly(ɛ-caprolactone-co-propargyl carbonate) grafted with poly(2-[dimethylamino]ethyl methacrylate) was synthesized by combining ring opening polymerization, azide-alkyne click reaction, and atom transfer radical polymerization (ATRP). Well-defined copolymers with a target composition and a tailored structure were achieved via the grafting from approach by using a single catalytic system for both click reaction and ATRP. Kinetic studies demonstrated the controlled/living character of the employed polymerization methods. The thermal properties and self-assembly in aqueous medium of the graft copolymers were dependent on their composition. The resulting polymeric materials showed low cytotoxicity toward L929 cells, demonstrating their potential for biomedical applications. This type of materials containing cationic side chains tethered to biocompatible and biodegradable segments could be the basis for promising candidates as drug and gene delivery systems.     

Syntheses and characterizations of poly[2‐(dimethylamino)ethyl methacrylate]–poly(propylene oxide)–poly[2‐(dimethylamino)ethyl methacrylate] ABA triblock copolymers

A novel, near‐monodisperse, well‐defined ABA triblock copolymer, poly[2‐(dimethylamino)ethyl methacrylate]‐b‐poly(propylene oxide)‐b‐poly[2‐(dimethylamino)ethyl methacrylate], was synthesized via oxyanion‐initiated polymerization. The initiator was a telechelic‐type potassium alcoholate prepared from poly(propylene glycol) and KH in dry tetrahydrofuran. The copolymers produced were characterized by Fourier transform infrared, ¹H NMR, and gel permeation chromatography (GPC). GPC and ¹H NMR analyses showed that the products obtained were the desired copolymers, with narrow molecular weight distributions (ca. 1.09–1.11) very close to that of the original poly(propylene glycol). ¹H NMR, surface tension measurements, and dynamic light scattering all indicated that the triblock copolymer led to interesting aqueous solution behaviors, including temperature‐induced micellization and very high surface activity. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 624–631, 2002; DOI 10.1002/pola.10144     

Synthesis and characterization of semi-interpenetrating polymer network based on poly(dimethylsiloxane) and poly[2-(dimethylamino)ethyl methacrylate]

A semi-interpenetrating polymer network (semi-IPN) based on poly(dimethylsiloxane) and poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) was prepared. The material obtained was characterized by infrared spectrometry, differential scanning calorimetry, thermogravimetric analysis and scanning electronic microscopy. The results indicated the presence of PDMAEMA into the semi-IPNs. Only the network with the highest amount of crosslinker [(3-chloropropyl)trimethoxysilane] was stable in water. To evaluate the hydrophilic/hydrophobic character of the obtained material, swelling measurements were performed for the stable network in water and in toluene. The semi-IPN was able to adsorb about 34 % in mass of water, indicating that an appropriate hydrophylic/hydrophobic balance was obtained. That behavior is desirable since the material was designed for metal adsorption from aqueous medium, without a lost in the ability to swell in less polar solvents.     

Synthesis and characterization of original 2-(dimethylamino)ethyl methacrylate/poly(ethyleneglycol) star-copolymers

Novel synthetic transfection vectors with linear triblock and star-shaped diblock copolymer architectures have been synthesized by atom transfer radical polymerization (ATRP). Based on 2-(dimethylamino)ethyl methacrylate (DMAEMA) and copolymerization with poly(ethyleneglycol) α-methoxy, ω-methacrylate (MAPEG), the synthesis was realized using CuBr ligated with 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA) as catalytic complex and either ethyl 2-bromoisobutyrate (EBⁱB) or bis(α-bromoisobutyryl) N-methyl diethanolamine (DEA) or tris(α-bromoisobutyryl) triethanolamine (TEA) as (multifunctional)initiator. The polymers were characterized by GPC and NMR. The solution properties of these homopolymers and palm-tree-like copolymers were investigated by viscometry either in pure water or in buffered aqueous solutions. Interestingly, all the synthesized polymers show polyelectrolyte effect in Millipore water (25 °C) and in Hepes (20 mM) buffer solution (pH 7.4, NaCl 155 mM, 25 °C). Fitting of these viscometric data according to either Fuoss or Fedors equation allows for calculating the intrinsic viscosity of the polymers. These results are compared with dynamic light scattering (DLS) experiments to determine absolute masses. Finally, DEA based palm-tree-like copolymer is investigated to AFM measurement and micelles were observed at pH 8.     

Solvent-free synthesis and purification of poly[2-(dimethylamino)ethyl methacrylate] by atom transfer radical polymerization

Solvent-free synthesis of well-defined poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) (co)polymers was performed by atom transfer radical polymerization conducted under very mild conditions (in bulk at 25 degrees C). The pH-dependence and the thermo-responsive behaviour of PDMAEMA in aqueous solution were operated to isolate and purify the (co)polymers without using any organic solvent or further catalyst extraction. The viscosity in aqueous solution of so-purified PDMAEMA homopolymers and their block copolymers with poly(ethylene glycol) (PEG) was studied as a function of molar mass and concentration and a typical polyelectrolyte behaviour was observed, these catalyst-deprived polycations are able to form stable and non toxic complexes with DNA, showing good transfection efficacies in gene therapy.     

Poly(2-[dimethylamino]ethyl methacrylate)-b-poly(hydroxypropyl methacrylate)/DNA polyplexes in aqueous solutions

This study involves the investigation of the complexation ability of poly(2-[dimethylamino]ethyl methacrylate)-b-poly(hydroxypropyl methacrylate) (PDMAEMA-b-PHPMA) amphiphilic pH and thermoresponsive block copolymers, and their quaternized counterparts QPDMAEMA-b-PHPMA, toward short DNA in aqueous solutions. The PDMAEMA-b-PHPMA amphiphilic block copolymers present various self-assembly characteristics when inserted into aqueous media, depending on the composition, the solubilization protocol, the acidity and the temperature of the aqueous media. Copolymer aggregates-DNA interactions and nanostructure formation after complexation are investigated by dynamic light scattering and intensity measurements in aqueous solutions in a fixed temperature range, utilizing two different solubilization protocols for the copolymers. Ethidium bromide assays by fluorescence spectroscopy and ζ-potential measurements were also utilized to investigate the structure and properties of the DNA/copolymer polyplexes. The interpretation of such physicochemical characterization provides extra comprehension of the novel (Q)PDMAEMA-b-PHPMA copolymers self-assembly characteristics and assesses their ability for DNA complexation, stabilization, and delivery.     

Thermosensitive behavior of poly(ethylene glycol)/poly(2‐(N,N‐dimethylamino)ethyl methacrylate) double hydrophilic block copolymers

The poly(ethylene glycol)/poly(2‐(N,N‐dimethylamino)ethyl methacrylate) (PEG/PDMAEMA) double hydrophilic block copolymers were synthesized by atom transfer radical polymerization using mPEG‐Br or Br‐PEG‐Br as macroinitiators. The narrow molecular weight distribution of PEG/PDMAEMA block copolymers was identified by gel permeation chromatography results. The thermosensitivity of PEG/PDMAEMA block copolymers in aqueous solution was revealed to depend significantly on pH, ionic strength, chain structure, and concentration of the block copolymers. By optimizing these factors, the cloud point temperature of PEG/PDMAEMA block copolymers can be limited within body temperature range (30–37 °C), which suggests that PEG/PDMAEMA block copolymers could be a good candidate for drug delivery systems. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 503–508, 2010     

Interaction of polymer and surfactant at the air-water interface: poly(2-(dimethylamino)ethyl methacrylate) and sodium dodecyl sulfate

The interactions between the weak polyelectrolyte, poly(2-(dimethylamino) ethyl methacrylate) or PDMAEMA, and the anionic surfactant sodium dodecyl sulfate (SDS) at the air-water interface have been investigated at pH = 3 and 9 using a combination of neutron reflectivity and surface tension measurements. By using deuterated PDMAEMA in combination with h-SDS and d-SDS, we have been able to directly determine the distribution of both the polymer and the surfactant at the air-water interface. At pH = 3, the polyelectrolyte is positively charged while at pH = 9 it is essentially uncharged. The enhancement in the adsorption of SDS at low coverage suggests that surface active polymer surfactant complexes are forming and adsorbing at the interface. This leads to close to monolayer adsorption of SDS, suggesting that it is surfactant monomers that are complexing with polymers that are in extended conformations parallel to the surface. As the concentration of SDS in the mixtures changes so does the surfactant content of the complexes, which affects the surface activity and hence the coverage of the complexes. Multilayer structures are formed at SDS concentrations of 0.1 and 1 mM, for pH = 3 and 9, respectively.     

Kinetics and mechanism of the grafting of 2-(dimethylamino)ethyl methacrylate onto hydrocarbon substrates

The kinetics of grafting a basic monomer, 2-(dimethylamino)-ethyl methacrylate (DMAEMA) to hydrocarbon substrates have been investigated. These systems were chosen as models for the grafting of a homopolymerizable monomer to polyolefins such as polyethylene. The reactions with squalane and n-eicosane were initiated by an organic peroxide, 2,5-dimethyl 2,5 dit-butylperoxy)-3-hexyne; grafting yields become significant at high reaction temperatures and low monomer concentrations. In squalane, the order of reaction with respect to monomer increased from about 1.1 for 0.22?0.44M DMAEMA to almost 2 at 0.69M DMAEMA; the order with respect to initiator was 0.56. The overall activation energy in the 130?160°C temperature range was, however, surprisingly low, 42±5 kJ mol^?1. When analytical data were used to separate the overall rate into those for grafting and homopolymerization, different kinetic paths were observed for the competing reactions. These results are interpreted in terms of two different mechanisms; intramolecular chain transfer plays an important role in grafting, while depropagation becomes a major factor in homopolymerization at temperatures above 150°C. © 1995 John Wiley & Sons, Inc.     

Microwave-Assisted Synthesis and Characterization of Poly(2-(dimethylamino)ethyl methacrylate) Grafted Gellan Gum

Poly(2-(dimethylamino)ethylmethacrylate) was grafted on gellan gum (GG) in aqueous medium under microwave irradiation using ammonium persulfate and N,N,N′N′-tetramethylethylenediamine as the initiation system. Grafted copolymers were characterized by FT-IR, TGA, and SEM techniques. The influence of microwave power, exposure time, and composition of the reaction mixture on extent of grafting was studied. Conditions for obtaining the highest degree of grafting were optimized. The rate of grafting was determined from weight measurements. The overall activation energy for grafting is found to be 31.2 kJ/mol, indicating the occurrence of the grafting process with absorption of low thermal energy.     

Conformational studies on the four stereoisomers of the novel anticholinergic 4-(dimethylamino)-2-phenyl-2-(2-pyridyl)pentanamide

Summary To interpret differences in the anticholinergic activity among the four steroisomers of 4-(dimethylamino)-2-phenyl-2-(2-pyridyl)pentanamide (1–4), we performed conformational studies using the semiempirical molecular orbital method. The structures of the global minimum-energy conformations obtained for 1–4, however, could not explain the different activities, particularly in terms of distances between the essential pharmacophores. We thus implemented superimposition studies, using the energetically stable conformations of the most active stereoisomer, 1(2S,4R), as a template. The energy penalties for a conformation change of the less active stereoisomers 2–4 from their global minimum-energy structure to a new conformation, fitting onto the global minimum-energy conformation of 1, appear to account for the differences in the pharmacological potency better than using the other conformations of 1 as a template. We thus presume that the global minimum-energy conformation of 1 is closely related to the bioactive conformation for these anticholinergics, and also that the pharmacological potency is linked to how readily these substances can change their conformations to fit the muscarinic receptor.     

Effect of reaction conditions on the grafting of 2-(dimethylamino)ethyl methacrylate onto hydrocarbon substrates

The grafting of 2-(dimethylamino)ethyl methacrylate (DMAEMA) onto two model hydrocarbons, squalane and n-eicosane, and to linear low density polyethylene (LLDPE) has been investigated. The results of the study indicate that a high reaction temperature, 160°C, and a low concentration of monomer, less than 0.3 M, are optimum conditions for the grafting reaction. Reaction products, which consisted of grafted hydrocarbons and poly(DMAEMA), were separated by solvent extraction and vacuum distillation; samples were then analyzed by NMR and FTIR spectroscopy and size exclusion chromatography. ¹H-NMR spectroscopy indicates that grafted squalane contained approximately 6 DMAEMA units per squalane residue. ¹H- and ¹³C-NMR and molecular weight studies strongly suggest that the grafts onto the model hydrocarbons consist of single DMAEMA units. Results of the melt grafting of DMAEMA onto LLDPE show that the grafting efficiency and degree of grafting are substantially lower than were expected from the model system. © 1994 John Wiley & Sons, Inc.     

Crystal structure of the benzene solvate of bis[2-(o-diphenylphosphorylphenoxy)ethyl] ether

Using x-ray diffraction analysis, we have determined the molecular structure of the phosphorus-containing podand bis[2-(o-diphenylphosphorylphenoxy) ethyl] ether in the crystal of its benzene solvate. We have established a considerable difference between the conformations of the free podand and its (previously studied) "guest—host" complex with an organic ammonium cation.Institute of Physiologically Active Substances, Russian Academy of Sciences, 142432 Chernogolovka. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 624–629, March, 1992.