- Vesicular assembly and thermo-responsive vesicle-to-micelle transition from an amphiphilic random copolymer
-
Vesicular assembly from a thermo-responsive amphiphilic random copolymer is reported. Vesicle-to-micelle transition above a critical morphology transition temperature (CMTT) resulted in selective triggered release of encapsulated hydrophilic guests over hydrophobic ones. The aggregation pattern of a control polymer indicated a defined role of the methacrylamide groups in the polymer backbone for such unprecedented self-assembly from a simple polymer.
- Dan, Krishna,Bose, Nivedita,Ghosh, Suhrit
-
-
Read Online
- Synthesis and single-chain folding of amphiphilic random copolymers in water
-
Amphiphilic random methacrylate copolymers, consisting of poly(ethylene glycol) (PEG) and alkyl pendent groups, undergo reversible single-chain self-folding in water via intramolecular hydrophobic interaction, to generate a dynamic unimolecular hydrophobic nanospace, similar in shape but structurally different relative to micelles and microgel star polymers. These copolymers were prepared by the ruthenium-catalyzed living radical copolymerization of a PEG methacrylate (PEGMA) and an alkyl methacrylate (RMA; R, -CnH 2n+1, n = 1-18), where copolymer composition, degree of polymerization, and hydrophobic R moiety were varied. Detailed structural and chain-folding characterization has revealed: single-chain folding is favored with the RMA content 20-40 mol % per chain; the hydrophobic inner compartment (or the self-folded structure) is stable even at a high polymer concentration (up to ～6 wt %); and folded-unfolded transition occurs on addition of methanol or by elevating solution temperature, finally to phase-separation above a lower critical solution temperature.
- Terashima, Takaya,Sugita, Takanori,Fukae, Kaoru,Sawamoto, Mitsuo
-
p. 589 - 600
(2014/02/14)
-
- Sulfonated polypyrene (S-PPR) as efficient catalyst for esterification of carboxylic acids with equimolar amounts of alcohols without removing water
-
Sulfonated polypyrene (S-PPR) efficiently catalyzed the reactions between carboxylic acids and equimolar amounts of alcohols with and without heptane to give the corresponding esters in good to excellent yields. Esterification was carried out at 110 °C without removing water. Transesterification of carboxylic esters with a slight excess of alcohols smoothly proceeded without heptane to give the corresponding esters in good yields. For these reactions, S-PPR was recycled without significant loss of activities.
- Tanemura, Kiyoshi,Suzuki, Tsuneo
-
p. 1972 - 1975
(2013/04/23)
-
- N-Butyl-2,4-dinitro-anilinium p-toluenesulfonate as a highly active and selective esterification catalyst
-
N-Butyl-2,4-dinitro-anilinium p-toluenesulfonate (1) was found to be a very active esterification catalyst that promotes condensation of equal mole amount of carboxylic acids and alcohols under mild conditions. This catalyst is also highly selective towards carboxylic acid and alcohol substrates at ambient temperature.
- Sattenapally, Narsimha,Wang, Wei,Liu, Huimin,Gao, Yong
-
supporting information
p. 6665 - 6668
(2013/11/19)
-
- Esterification catalysis by pyridinium p -toluenesulfonate revisited - Modification with a lipid chain for improved activities and selectivities
-
The lipid analogs of pyridinium p-toluenesulfonate (PPTS) were examined for catalysis of the condensation of an equimolar mixture of carboxylic acids and alcohols under mild conditions without removal of water. Although PPTS is a poor catalyst, the introduction of a lipid chain and nitro group significantly improved the activity of PPTS and led to selectivity at suppressing the elimination side reactions of alcohols. 2-Oleamido-5-nitro-pyridinium p-toluenesulfonate (6) is a lead catalyst that promoted various esterification reactions with yields up to 99%.
- Wang, Wei,Liu, Huimin,Xu, Shaoyi,Gao, Yong
-
p. 2906 - 2912
(2013/09/02)
-
- Mild, powerful, and robust methods for esterification, amide formation, and thioesterification between acid chlorides and alcohols, amines, thiols, respectively
-
We developed two efficient practical methods for esterification, amide formation, and thioesterification between acid chlorides and alcohols, amines, thiols, respectively. The present mild and robust reaction was performed by two separate methods both by combining cheap and readily available amines, N-methylimidazole, and N,N,N′,N′-tetramethylethylenediamine (TMEDA). Method A uses catalytic N-methylimidazole and TMEDA with an equimolar amount of K2CO3, whereas Method B uses equimolar amounts of N-methylimidazole and TMEDA. The salient features are as follows. (i) With regard to reactivity, Method B was superior to Method A for esterification and thioesterification, whereas cost-effective Method A was superior to Method B for amide formation. (ii) Amide formation proceeded smoothly between acid chlorides and less nucleophilic and stereocongested amines such as 2,6-dichloroaniline. (iii) This protocol was applied to the successful synthesis of two agrochemicals, bromobutide and carpropamid.
- Nakatsuji, Hidefumi,Morimoto, Mami,Misaki, Tomonori,Tanabe, Yoo
-
p. 12071 - 12080
(2008/03/13)
-
- Water solvent method for esterification and amide formation between acid chlorides and alcohols promoted by combined catalytic amines: Synergy between N-methylimidazole and N,N,N′,N′-tetramethylethylenediamine (TMEDA)
-
An efficient method for esterification between acid chlorides and alcohols in water as solvent has been developed by combining the catalytic amines, N-methylimidazole and N,N,N′,N′-tetramethylethylenediamine (TMEDA). The present Schotten-Baumann-type reaction was performed by maintaining the pH at around 11.5 using a pH controller to prevent the decomposition of acid chlorides and/or esters and to facilitate the condensation. The choice of catalysts (0.1 equiv.) was crucial: the combined use of N-methylimidazole and TMEDA exhibited a dramatic synergistic effect. The catalytic amines have two different roles: (i) N-methylimidazole forms highly reactive ammonium intermediates with acid chlorides and (ii) TMEDA acts as an effective HCl binder. The production of these intermediates was rationally supported by a careful 1H NMR monitoring study. Related amide formation was also achieved between acid chlorides and primary or secondary amines, including less nucleophilic or water-soluble amines such as 2-(or 4-)chloroaniline, the Weinreb N-methoxyamine, and 2,2-dimethoxyethanamine.
- Nakatsuji, Hidefumi,Morita, Jun-Ichi,Misaki, Tomonori,Tanabe, Yoo
-
p. 2057 - 2062
(2007/10/03)
-
- Acylation of alcohols and amines with vinyl acetates catalyzed by Cp*2Sm(thf)2
-
Cp*2Sm(thf)2 was found to be an efficient catalyst for the acylation of alcohols and amines with esters under mild conditions. In the present acylation, vinyl and isopropenyl acetates served as good acylating agents. Thus, a variety of alcohols and amines underwent acylation with vinyl and isopropenyl acetates in the presence of Cp*2Sm(thf)2 to give the corresponding esters and amides in good to excellent yields. This catalytic acylation of alcohols and amines offers an additional useful method by the use of various esters, instead of acid anhydrides and acid chlorides, as acylating agents under very mild conditions.
- Ishii, Yasutaka,Takeno, Mitsuhiro,Kawasaki, Yumi,Muromachi, Akifumi,Nishiyama, Yutaka,Sakaguchi, Satoshi
-
p. 3088 - 3092
(2007/10/03)
-
- Cosmetic emulsions containing acrylamide copolymer
-
Water-in-oil emulsions wherein the emulsifier is a copolymer of 1 mol of acrylamide with 2 to 20 mols of at least one ethylenically unsaturated ester copolymerizable therewith selected from the group consisting of vinyl alkylcarboxylates, alkyl and cycloalkyl acrylates, and alkly and cycloalkyl methacrylates, wherein the alkyl and cycloalkyl groups contain 6 to 24 carbon atoms, and the continuous phase is a cosmetically acceptable oil, which can be prepared easily, safely and inexpensively. The emulsions are substantially odorless and are cosmetically acceptable for the care of the skin.
- -
-
-
