Copolymeric nano/microgels of N-isopropylacrylamide and carboxyalkyl methacrylamides: Effect of methylene chains and the ionization state of the weak acids on size and sensitivity to pH and temperature

ABSTRACT

We prepared nano/microgels by precipitation copolymerization of N-isopropylacrylamide (NIPAAm), and one of three different carboxyalkyl methacrylamides [methacryloylamido hexanoic acid (M₅), 8-methacryloylamido octanoic acid (M₇), and 11-methacryloylamido undecanoic acid (M₁₀)], either in the acid forms or as carboxylates (potassium salts). The hydrodynamic diameter (Dh) of the nano/microgels prepared with the carboxylates was smaller (≈100 nm for M₁₀ copolymers), compared to the size of homopolymeric NIPAAm microgels prepared by dispersion polymerization (around 600 nm), indicating that the carboxylates act as surfactants reducing the size of the seeds during the polymerization process. These materials presented a swollen-shrunken transition temperature (T _tr) similar to the T _tr of the homopolymeric NIPAAm microgels, without pH sensitivity. On the other hand, the copolymeric microgels prepared from the acid form of the comonomers have a similar or bigger size than NIPAAm microgels. For these copolymers, the T _tr can be tuned by the type and proportion of acid comonomer used and present pH sensitivity. This is important for biomedical applications such as positive temperature control release. Polyelectrolyte titration demonstrates that the nano/microgels prepared with the carboxylates behave as hard spheres, while the microgels prepared with the weak acid behave as porous materials.     

Tight binding of poly(carboxylate) ligand to calcium carbonate with intramolecular NH…O hydrogen bond

Novel poly(carboxylates), partially amidated poly(acry late), poly{[1-carboxylate-2-(N-t-butyl)carbamoyl)]ethylene-alt-ethylene}, poly[1-(N-oxysuccinyl-aminomethenyl)ethylene], poly[1-(N-oxymalenyl-aminomethnyl)ethylene] and poly[1-(N-oxyphthalyl-aminomethnyl)ethylene] with intramolecular NH…O hydrogen bond between amide NH and coordinating oxygen were synthesized as model ligands for CaCO₃ biominerallization. The FE/SEM and its backscatter of the CaCO₃ composite of gold colloid-conjugated poly{[1-carboxylate-2-(N-p-methylthiophenyl)carbamoyl]ethylene-alt-ethylene} indicate that the polymer ligand is located at the surface of vaterite crystals and the oriented carboxylate ligands control the CaCO₃ polymorph.     

Metal complexes of macrocyclic ligands. Part XXIII. Synthesis,properties, and structures of mononuclear complexes with 12- and 14-membered tetraazamacrocycle-N,N′,N″,N‴-tetraacetic Acids

The two tetraazamacrocycle-N,N′,N″,N?-tetraacetic acids H₄dota and H₄teta form with Ni²⁺, Cu²⁺, and Zn²⁺ (M²⁺) mononuclear complexes MLH₂ and M′[ML], M′ being an alkaline earth ion. The structures of Ni(H₂dota) and Cu(H₂dota) have been solved by X-ray structure analysis. The metal ions are in a distorted octahedral geometry coordinated by four amino N-atoms and two carboxylates. In the case of Cu²⁺, the distortions are more pronounced than for Ni²⁺ indicating that the Jahn-Teller effect is operating. Starting from these two structures, the coordination geometry of the other complexes is discussed using VIS and IR spectra.     

Synthesis of dimeric estradiol enzyme model containing imidazolyl and study on its catalytic efficiency in hydrolysis of carboxylates and phosphates

Dimeric estradiol enzyme model (2) was synthesized by etherification of 2,4-bis(N-imidazolylmethyl)-17β-estradiol (1) with 1,3-dibromopropane in the presence of anhydrous K2CO3. Hydrolysis of carboxylates and phosphates catalyzed by the model showed Michaelis-Menten kinetic behavior. Hydrophobic interaction between the model and ester accelerates the hydrolysis markedly, rate enhancement of up to 65 and 285 fold, relative to imidazole, is observed.     

Reaction of N-hydroxymethylsaccharin with aliphatic carboxylic acid derivatives: Synthesis of N-acylsaccharins and N-(saccharinylmethyl) aliphatic carboxylates

N-Acylsaccharins and N-(saccharinylmethyl)aliphatic carboxylates were synthesized from N-hydroxymeth-ylsaccarin and aliphatic carboxylic acid chlorides (or anhydrides).     

Preparation of Complexes of Nickel(II) Aryl Carboxylates with Morpholine and Piperidine

Complexes of nickel(II) aryl carboxylates with a general formula Ni(RC₆H₄COO)₂L₂ where R=H, p-CH₃. p-Cl, m- & p-NO₂; and L = morpholine and piperidine; have been prepared by the interaction of nickel(II) aryl carboxylates with a large excess of appropriate amine. Unlike parent anhydrous nickel(II) aryl carboxylates all these complexes are soluble in common organic solvents.     

A synthesis of potential new antiarrhythmic agents

N‐Ethylation of substituted ethyl 1H‐indole‐2‐carboxylates with iodoethane and potassium carbonate gave substituted ethyl 1‐ethyl‐1H‐indole‐2‐carboxylates. The later compounds on treatment with a range of aryl amines with varying structural complexity, gave the desired ethyl 1H‐indole‐2‐carboxamide analogues.     

The Synthesis of Some Novel 1,2‐Dihydroisoquinoline Derivatives

Treatment of methyl 2‐aryl‐1,2,3,4‐tetrahydroisoquinoline‐3‐carboxylates 5 with N‐bromosuccinimide followed by heating in the presence of an acid catalyst resulted in the formation of the corresponding methyl 2‐aryl‐1,2‐dihydroisoquinoline‐3‐carboxylates 10 via an oxidation–dehydration sequence.     

1,3,2-Oxazaphosphinane analogs of phosphorylacetic acid derivatives: synthesis and properties

Reactions of 2-AlkO-1,3,2-oxazaphosphinanes with alkyl N-haloacetylamino or N-chloromethyl-N-methoxycarbonylamino carboxylates mainly give products with retention (Alk = Me) and opening of the ring (Alk = Et). In aqueous solution, cyclic products with the N-isopropyl group are only stable, while the rest undergo hydrolysis with cleavage of the P-N bond of the ring. Oxazaphosphinane analogs of phosphorylacetamide and phosphorylacetohydrazide were synthesized.     

Photolysis of light-transforming polymer material

Light-transforming polymer materials activated with the compositions on the basis of the europium carboxylates with different ligands and anthranilic acid exhibiting the intense luminescence in the spectral range 400–700 nm are prepared. It is shown that light stability of polymer materials on the basis of the aboveprepared compositions is higher than of polymer materials activated with the europium salts. The photolysis of luminescent polymers was studied. For the compositions EuL₃C₁₃H₁₃N₃·xH₂O + anthranilic acid gradual increase in the luminescence intensity of the europium ion is marked.     

Preparation of Complexes of Copper (II) Aryl Carboxylates with Morpholine

Complexes of copper (II) aryl carboxylates with morpholine were prepared by the interaction of the copper carboxylate with the morpholine equimolar as well as in large excess quantities in acetone medium. The complexes isolated correspond to 1:1 and 1:2 stoichiometry. In continuation of our work on the preparation of complexes of copper (II) aryl carboxylates with nitrogen donors like aliphatic amines,¹⁾ heterocyclic amines²⁾ and pyridine–N–Oxide³⁾, the present communication deals with the preparation of complexes of copper (II) aryl carboxylates with morpholine.     

Geminal systems. 50. Synthesis and alcoholysis of N-acyloxy-N-alkoxy derivatives of ureas,carbamates, and benzamides

Procedures were developed for the synthesis of N-acyloxy-N-alkoxy derivatives of ureas, carbamates, and benzamides by the reactions of the corresponding N-alkoxy-N-chloro derivatives with sodium carboxylates in MeCN. N-Chloro-N-ethoxy-p-toluenesulfonamide was inert in this reaction. Alcoholysis of N-acyloxy-N-alkoxy derivatives of ureas, carbamates, and tert-alkylamines afforded the corresponding N,N-dialkoxy derivatives, whereas alcoholysis of N-acetoxy-N-ethoxybenzamide gave rise to alkyl benzoates.     

An Efficient Route to Ethyl 5‐Alkyl‐ (Aryl)‐1H‐1,2,4‐triazole‐3‐carboxylates

An efficient general route to the synthesis of 5‐substituted 1H‐1,2,4‐triazole‐3‐carboxylates was developed. N‐acylamidrazones were obtained from carboxylic acid hydrazides and ethyl thiooxamate or ethyl 2‐ethoxy‐2‐iminoacetate hydrochloride and then were reacted with chloroanhydride of the same carboxylic acid. As the next step, diacylamidrazones were cyclized to 5‐substituted 1H‐1,2,4‐triazole‐3‐carboxylates one pot in mild conditions.     

A silaproline‐containing dipeptide

The silaproline‐containing dipeptide N‐(3,3‐di­methyl‐1‐pivaloyl‐1‐aza‐3‐sila‐5‐cyclo­pentyl­carbonyl)‐l ‐alanine iso­propyl­amide, C₁₇H₃₃N₃O₃Si, has two independent molecules in the asymmetric unit and each adopts a β‐II folded conformation, where the amide on the terminal C interacts intramolecularly with the pivaloyl O atom. The five‐membered silaproline ring is C^β‐puckered, an infrequent conformation for the homol­ogous proline ring.     

(2S)‐1‐Carbamoylpyrrolidine‐2‐carboxylic acid

In the title compound, also known as N‐carbamoyl‐l ‐proline, C₆H₁₀N₂O₃, the pyrrolidine ring adopts a half‐chair conformation, whereas the carboxyl group and the mean plane of the ureide group form an angle of 80.1 (2)°. Molecules are joined by N—H...O and O—H...O hydrogen bonds into cyclic structures with graph‐set R²₂(8), forming chains in the b‐axis direction that are further connected via N—H...O hydrogen bonds into a three‐dimensional network.     

Oxygenase‐Catalyzed Desymmetrization of N,N‐Dialkyl‐piperidine‐4‐carboxylic Acids

γ‐Butyrobetaine hydroxylase (BBOX) is a 2‐oxoglutarate dependent oxygenase that catalyzes the final hydroxylation step in the biosynthesis of carnitine. BBOX was shown to catalyze the oxidative desymmetrization of achiral N,N‐dialkyl piperidine‐4‐carboxylates to give products with two or three stereogenic centers.     

A dual functional 1D Cd-based coordination polymer for the highly luminescent sensitive detection of Fe3+ and picric acid

Fluorescent coordination polymers have drawn extensive attention in sensing applications. Herein, we report a carbazole-based one-dimensional coordination polymer [CdL(H₂O)(DMF)₂]·DMF ( CdL , H₂L = 9H-carbazole-2,7-dicarboxylic acid, DMF = N,N-dimethylformamide). In CdL , each Cd²⁺ ion is four-bridged by carboxylates, which is further linked by the carbazole units to form a one-dimensional Cd–O–C chains along the c-axis. CdL displays high water stability in the pH range of 3–10. Luminescence experiments indicate that CdL could selectively detect Fe³⁺ during the concentration range of 0–0.1 mm in water with a K_sv of 8022 m ⁻¹ and picric acid (PA) within the concentration range of 0–0.05 mm in methanol solution with a K_sv of 17948 m ⁻¹ respectively. The above results reveal that CdL can be applied as a multiresponse luminescence sensor for selectively sensing for Fe³⁺ in water and PA in methanol solution.     

2-Azabicyclo[2.2.1]heptane-3-carboxylic acid - A bicyclic proline

Diels-Alder reaction of cyclopentadiene and methyl N-carbobenzyloxy-2-iminoacetate generated in situ from methyl 2-chloro-N-carbobenzyloxyglycinate by triethylamine gave the N-carbobenzyloxy unsaturated bicyclic proline ester. This was converted in two steps to 2-azabicylo[2.2.1]heptane-3-carboxylic acid. In contrast to N-carbobenzyloxy-L-proline methyl ester, the corresponding bicyclic proline ester was resistant to hydrolysis catalyzed by carboxypeptidase Y.     

μ-oxo, μ-sulphido complexes of oxomolybdenum(V) with carboxylate ligands

Summary We report the synthesis and study of new Mo(V) dimeric complexes with oxosulphido bridges andn-pentyl,n-hexyl,n-heptyl,iso-octyl, cyclohexyl and phenyl carboxylates as coligands. The complexes, of general formula Mo₂O₃S(RCO₂)₂, are compared to the Mo^v carboxylates with monoxo and dioxo bridges. Their i.r. and electronic spectra are sensitive to substitution of sulphur atoms in the bridge system. The results are discussed in the light of the structural information available for oxomolybdenum(V) complexes.     

Synthesis of three‐armed poly(trans‐4‐hydroxy‐N‐benzyloxycarbonyl‐L‐proline)‐block‐poly(ε‐caprolactone) copolymers

A series of novel types of three‐armed poly(trans‐4‐hydroxy‐N‐benzyloxycarbonyl‐L ‐proline)‐block‐poly(ε‐caprolactone) (PHpr‐b‐PCL) copolymers were successfully synthesized via melt block copolymerization of trans‐4‐hydroxy‐N‐benzyloxycarbonyl‐L ‐proline (N‐CBz‐Hpr) and ε‐caprolactone (ε‐CL) with a trifunctional initiator trimethylolpropane (TMP) and stannous octoate (SnOct₂) as a catalyst. For the homopolycondensation of N‐CBz‐Hpr with TMP initiator and SnOct₂ catalyst, the number‐average molecular weight (M_n) of prepolymer increases from 530 to 3540 g mol^?1 with the molar ratio of monomer to initiator (3–30), and the molecular weight distribution (M_w/M_n) is between 1.25 to 1.32. These three‐armed prepolymer PHpr were subsequently block copolymerized with ε‐caprolactone (ε‐CL) in the presence of SnOct₂ as a catalyst. The M_n of the copolymer increased from 2240 to 18,840 g mol^?1 with the molar ratio (0–60) of ε‐CL to PHpr. These products were characterized by differential scanning calorimetry (DSC), ¹H NMR, and gel permeation chromatography. According to DSC, the glass‐transition temperature (T_g) of the three‐armed polymers depended on the molar ratio of monomer/initiator that were added. In vitro degradation of these copolymers was evaluated from weight‐loss measurements and the change of M_n and M_w/M_n. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1708–1717, 2005