Search results for "polymerization"

Dynamic Light Scattering Investigation of the Kinetics and Fidelity of Supramolecular Copolymerizations in Water

2017

The self-assembly of supramolecular copolymers facilitates the preparation of multifunctional materials, with tunable mechanical, electronic, or bioactive properties. Compared to covalent copolymerization protocols, controlling the molecular weight, stability, and monomer sequence of a multicomponent supramolecular copolymer remains limited. Here, we report a light scattering investigation of the charge-regulated supramolecular copolymerization in neutral buffer of physiological ionic strength, supported with electron microscopy and circular dichroism spectroscopy experiments. Dendritic anionic and cationic peptide comonomers self-assemble into AB-type heterocopolymers with a nanorod-like m…

Circular dichroism of polynucleotides: Interactions of NiCl2 with poly(dA-dT).poly(dA-dT) and poly(dG-dC).poly(dG-dC) in a water-in-oil microemulsion.

2008

The thermal behavior of the synthetic, high molecular weight, double stranded polynucleotides poly(dA-dT)·poly(dA-dT) [polyAT] and poly(dG-dC)·poly(dG-dC) [polyGC] solubilized in the aqueous core of the quaternary water-in-oil cationic microemulsion CTAB|n-pentanol|n-hexane|water in the presence of increasing amounts of NiCl2 at several constant ionic strength values (NaCl) has been studied by means of circular dichroism and electronic absorption spectroscopies. In the microemulsive medium, both polynucleotides show temperature-induced modifications that markedly vary with both Ni(II) concentration and ionic strength. An increase of temperature causes denaturation of the polyAT duplex at lo…

Supramolecular polymerization of sulfated dendritic peptide amphiphiles into multivalent L-selectin binders

2021

The synthesis of a sulfate-modified dendritic peptide amphiphile and its self-assembly into one-dimensional rod-like architectures in aqueous medium is reported. The influence of the ionic strength on the supramolecular polymerization was probed via circular dichroism spectroscopy and cryogenic transmission electron microscopy. Physiological salt concentrations efficiently screen the charges of the dendritic building block equipped with eight sulfate groups and trigger the formation of rigid supramolecular polymers. Since multivalent sulfated supramolecular structures mimic naturally occurring L-selectin ligands, the corresponding affinity was evaluated using a competitive SPR binding assay…

Two Latent and Two Hyperstable Polymeric Forms of Human Neuroserpin

2010

AbstractHuman neuroserpin (hNS) is a serine protease inhibitor that belongs to the serpin superfamily and is expressed in nervous tissues. The serpin fold is generally characterized by a long exposed loop, termed the reactive center loop, that acts as bait for the target protease. Intramolecular insertion of the reactive center loop into the main serpin β-sheet leads to the serpin latent form. As with other known serpins, hNS pathological mutants have been shown to accumulate as polymers composed of quasi-native protein molecules. Although hNS polymerization has been intensely studied, a general agreement about serpin polymer organization is still lacking. Here we report a biophysical chara…

ChemInform Abstract: A New Palladium(II)-Catalyzed [3,3] Aza-Claisen Rearrangement of 3-Allyloxy-5-aryl-1,2,4-oxadiazoles.

2011

Substituted derivatives such as (Ib,c) react with very high degree of stereochemistry explained by a cationic palladacycle intermediate similar to the one postulated for the Cope-rearrangement of 1,5-dienes.

Molecular Classification of 5-Amino-2-Aroylquinolines and 4-Aroyl-6,7,8-Trimethoxyquinolines as Highly Potent Tubulin Polymerization Inhibitors

2013

Algorithms for classification and taxonomy are proposed based on criteria as information entropy and its production. It is classified a series of 5-amino-2-aroylquinolines (AAQs) and 4-aroyl-6,7,8-trimethoxyquinolines (TMQs) combretastatin analogues for anti-cancer activity. 5-Amino-6-methoxy-2-aroylquinoline AAQ showed anti-proliferative activity more potent as compared to combretastatin A-4 (CA4), against various human cancer cell lines and a multidrug resistance (MDR) cancer cell line. On the basis of AAQ/TMQ structure–activity relationship new derivatives are designed. The AAQs/TMQs are classified using nine characteristic chemical properties in molecules. Many classification algorithms…

Long-Chain Branched Poly(Lactide)s Based on Polycondensation of AB2 -type Macromonomers

2012

A series of long-chain branched poly(d-/l-lactide)s is synthesized in a two-step protocol by (1) ring-opening polymerization of lactide and (2) subsequent condensation of the preformed AB2 macromonomers promoted by different coupling reagents. The linear AB2 macromonomers are prepared by Sn(Oct)2-catalyzed ROP of D- and L-lactide with 2,2-bis(hydroxymethyl)butyric acid (BHB) as an initiator. Optimization of the polymerization conditions allows for the preparation of well-defined macromonomers (Mw/Mn = 1.09–1.30) with adjustable molecular weights (760–7200 g mol−1). The two-step approach of the synthesis comprises as well the coupling of these AB2 macromonomers and hence allows precise contr…

Suzuki polycondensation with a hairpin monomer.

2009

Two straight monomers were subjected to an AA/BB-type Suzuki polycondensation with a hairpin-shaped 1,8-anthrylene monomer as the counterpart leading to a novel polyarylene which should have the preferred conformation of a folded chain. The molar masses were determined by gel permeation chromatography and dynamic light scattering and found to be M(w) = 14,000 and M(n) = 7,000. MALDI-TOF MS analysis of a fraction provides a fingerprint of the step-growth nature of this polymerization.

A PH-functionalized polyphosphazene: a macromolecule with a highly flexible backbone.

2006

Aliphatic Hyperbranched Copolyesters by Combination of ROP and AB2-Polycondensation

2005

Hyperbranched aliphatic copolyesters have been prepared by the copolymerization of e-caprolactone and 2,2-bis(hydroxymethyl)butyric acid (AB 2 -monomer), catalyzed by (i) HfCl 4 (THF) 2 and (ii) diphenylammonium trifluoromethanesulfonate (DPAT), respectively. In both cases, copolymerization by combined ROP/AB 2 -Polycondensation was achieved. The degree of branching (DB) and consequently the density of functional groups of the resulting copolyesters were controlled by the comonomer ratio in the feed. Molecular weights in the range M n =22 000-166 000 g mot -1 (GPC, PS standards) were obtained, with apparent polydispersity indices of 1.20 to 1.95. The DB was in the range 0.03-0.35. Remarkabl…