Search results for "Leche"

Telechele des methylpropens durch kationische polymerisation

1986

Amorcage par des hydrocarbures aromatiques et aliphatiques contenant des groupes terminaux chlorure d'isopropyle, associes a du trichlorure de bore. Mecanisme. Recyclage du coamorceur et du solvant

Hetero-Multifunctional Poly(ethylene glycol) Copolymers with Multiple Hydroxyl Groups and a Single Terminal Functionality

2009

Hetero-multifunctional poly(ethylene glycol-co-glycerol) random copolymers with multiple hydroxyl functionalities and a single terminal functionality have been prepared by copolymerization of ethylene oxide (EO) and ethoxy ethyl glycidyl ether (EEGE) with the use of a suitable initiator, introducing a protected amino group or a double bond, respectively. Acidic deprotection was used for removal of the acetal protecting groups in the chain, and the terminal amino group was regenerated by catalytic hydrogenation. A series of copolymers with narrow polydispersity was obtained, varying comonomer fractions from 3 to 67% and molecular weights in the range of 5 000-32 000 g · mol(-1) (1.05 < $\ove…

Networks of Partially Hydrogenatedcis-1,4-Polybutadiene and ‘Rigid Rods’

1996

Networks of 'flexible' and 'rigid' chains were synthesized. As 'flexible' component we have used different partially hydrogenated cis-1,4-polybutadiene. The 'rigid' component was synthesized from bis(1,2,4-triazoline-3,5-dione)s and biscyclohexadienes via repetitive Diels-Alder reaction. A slight excess of bis(1,2, 4-triazoline-3,5-dione)s leads to polymers with 1,2,4-triazoline-3,5-dione end groups, which can easily react with the partially hydrogenated cis-1,4-polybutadiene. The influence of the extent of hydrogenation and the amount of crosslinker on the mechanical and thermal behaviour is described.

Synthesis of new polymers via Diels–Alder reaction. III. Biscyclohexadienephthalimides as dienes

1993

Difunctional cyclohexadienes with dihydrophthalimide central unitsand phenyl side groups to increase solubility are used as bisdienes in repetitive Diels-Alder polyadditions with bis(4-(1,2,4,-triazoline-3,5-dione-4-yl)phenyl)methane as a difunctional dienophile. The polymers show good solubility in CH 2 Cl 2 and CHCl 3 . Non-stoichiometric Diels-Alder polyaddition with slight excess of the bistriazolinedione provides the possibility of synthesizing telechelics with highly reactive triazolinedione end groups

Heterotelechelic Ring-Opening Metathesis Polymers

2009

By combining sacrificial synthesis with the vinyl lactone termination technique, heterotelechelic polymers were synthesized. The nonterminating nature of sacrificial synthesis was utilized to introduce a hydroxyl group at the start of the polymer chain. Lactone termination was used to functionalize the chain ends with aldehydes or carboxylic acids. The synthesis of well-defined heterotelechelic polymers was thus accomplished employing the Grubbs’ first generation catalyst as the initiator. The living nature of this polymerization allowed for precise control over the molecular weight and guaranteed full functionalization of both polymer chain ends. The presence of the functional groups is sh…

Synthesis of Heterotelechelic α,ω Dye-Functionalized Polymer by the RAFT Process and Energy Transfer between the End Groups

2009

The synthesis of a vinyl polymer with two different fluorescent dye end groups using reversible addition-fragmentation chain transfer (RAFT) polymerization is described. Use of a pentafluorophenyl (PFP) activated ester chain transfer agent (CTA) provided a polymer with an R end group that was reactive toward amines and a dithioester ω end group. The R PFP ester was amidated with Oregon Green Cadaverin. This did not harm the ω dithioester, which was subsequently aminolyzed with an excess of n-propylamine in the presence of Texas Red-2-sulfonamidoethyl methanethiosulfonate, resulting in a disulfide bond connecting the second dye to the polymer chain. Excess dyes and side products were removed…

Sacrificial Synthesis of Hydroxy-Telechelic Metathesis Polymers via Multiblock-Copolymers

2009

The synthesis of well-defined telechelic ring-opening metathesis polymers has been achieved by Sacrificial Synthesis. With the formation of cleavable triblock-copolymers, precise control over the molecular weight and the degree of functionalization was achieved. Introducing cleavable monomers that can be addressed separately, sequential deprotection was accomplished which opened the path to more sophisticated polymeric materials bearing different substituents at their respective chain ends. Sacrificial penta- and heptablock-copolymers are also presented which allow the synthesis of well-defined telechelic polymers in good yields and significantly improved initiator efficiency.

1991

Telechelic α,ω-macrozwitterions — narrowly distributed polystyrene chains oppositely charged at each end — were synthesized via anionic polymerization using direct functionalization with the initiator and the termination agent. The resulting products were purified (zwitterion content ≥ 0,95) and characterized with gel permeation chromatography, viscometry, static and dynamic light scattering and small-angle neutron scattering. In unpolar solvents as toluene, the polymeric zwitterions form clusters with molecular weights depending on concentration. In the dilute case, the clusters are relatively small and consist of approximately 8 zwitterions. The structure of these clusters is discussed by…

1992

A series of copolymers are synthesized by repetitive Diels-Alder polyaddition reaction of bifunctional cyclohepta-1,3,5-trienes with bifunctional 1,2,4-triazoline-3,5-diones. The copolymers of different bistriazolinediones with a bisdiene, or of different biscycloheptatrienes with a dienophile, have good solubility in CH2Cl2 and CHCl3, while the homopolymers are poorly soluble. The copolymers were characterized by standard analytical techniques to test the structural regularity of these systems. Due to the kinetic control, it is possible to apply copolymerization statistics to these systems. Based on a model study, it is concluded that alipatic and aromatic bistriazolinediones have the same…

A propósito de la localización de una pintura sobre tabla de ?La Virgen de la Leche?, del siglo XIV, atribuida a Bernabé de Módena, que perteneció al…

2020

The castle's Hermitage of Yecla (Region of Murcia) constituted during the 13th to 16th centuries the first parish of the population, hosting a triptych-shaped altarpiece presided over by a tempera painting on wood of Our Lady of Humility or "Virgo Lactans", dated around 1370 and attributed to the painter Barnaba da Modena, which was the titular image of the mentioned temple under the title of Our Lady of the Incarnation, until at the end of the 18th century it changed ownership for the Conception of Our Lady. The table at averages of the eight hundred was placed in an a loft, appropriating it at the beginning of the 20th century by the retired military Pascual Spuche y Lacy, who sold it aro…