Search

Emerging dendritic-linear-dendritic (DLD) hybrids that possess synergetic properties of linear and highly functional branched dendritic polymers are becoming important macromolecular scaffolds in f ...

By taking advantage of the orthogonal nature of thiol−ene coupling and anhydride based esterification reactions, a facile and chemoselective strategy to dendritic macromolecules has been developed. The ability to interchange growth steps based on thiol−ene and anhydride chemistry allows the synthesis of fifth-generation dendrimers in only five steps and under benign reaction conditions. In addition, the presented coupling chemistries eliminate the traditional need for protection/deprotection steps and afford dendrimers in high yield and purity. The modularity of this strategy coupled with the latent reactivity of the alkene/hydroxyl chain ends was demonstrated by using different cores (alkene and hydroxyl functional), various AB2 and CD2 monomers and a range of chain end groups. As a result, three dendritic libraries were prepared which exhibited tunability of both the chemical functionality and physical properties including the fabrication of PEG hydrogels.

The preparation and characterization of a series of first to fourth generation dendronized poly-(norbornene)s are presented. The monomers were synthesized in a divergent fashion from 5-norbornene-2 ...

A divergent approach to synthesize dendritic aliphatic polyester structures based on 2,2-bis(hydroxymethyl) propionic acid (bis-MPA) is described. The key building block is the anhydride of isoprop ...

Liquid crystalline dendrimers with peripheral mesogen-containing units have been prepared. Multistep synthesis with several selective reactions was used in the preparation of the mesogen-containing ...

The cationic ring-opening polymerization of 3-ethyl-3-(hydroxymethyl)oxetane to form hyperbranched polyethers has been studied. The polymerizations have been performed in bulk using sulfonium salt initiators. To produce polymers of different degrees of branching, the reaction conditions (reaction temperature and initiator) have been varied. Polymerizations have also been performed in the presence of a trifunctional core molecule, trimethylolpropane. The conversion of monomer turned out to be the main factor determining the degree of branching in the resulting polymer. Polymers with degrees of branching ranging from 0.15 to 0.41 were synthesized. When 3-ethyl-3-(hydroxymethyl)oxetane was polymerized by slow addition of monomer to a core molecule, a lower degree of branching was obtained compared to the one-step synthesis with full conversion of monomer. The polydispersity was generally slightly lower when a core molecule was used than in the one-step homopolymerization of 3-ethyl-3-(hydroxymethyl)oxetane.

The preparation and characterization of a series of novel ferroelectric liquid crystalline dendrimers are presented. End-capping of 1-, 2-, and 3-generation dendrimers based on 2,2-bis(hydroxymethyl)propionic acid with mesogens gave surface-functionalized liquid crystalline compounds with 6, 12, and 24 mesogen-containing units, respectively. 4 -((R)-1-Methylheptyloxy)phenyl 4-(4 '-[10(hydroxycarbonyl)decyloxyl phenyl)benzoate was synthesized and used as a mesogen-containing unit. The purity and structure of each compound were determined by H-1 NMR spectroscopy, size exclusion chromatography, and elemental analysis. Differential scanning calorimetry and optical microscopy were used to investigate the mesomorphic properties of the mesogen-functionalized dendrimers. The materials displayed a variety of mesophases, including the smectic C* phase. All the liquid crystalline dendrimers showed ferroelectricity, and tilt angle and spontaneous polarization measurements were performed. The obtained results show that the ferroelectric properties of the materials are independent of the generation number of the dendritic scaffold.

Low-loss optical waveguides have been fabricated from fluorinated copolymers designed to incorporate photochemical amplification based on acid catalysis. Core and cladding layers were made, for single-mode (SM) channel waveguides, from the poly(pentafluorostyrene-co-glycidyl methacrylate) copolymer series and, for multimode (MM) ridge waveguides, from poly(tert-butyl methacrylate-co-glycidyl methacrylate) as the cladding and poly(pentafluorostyrene-co-glycidyl methacrylate) as core layer. The reactivity ratios for PFS and GMA monomers have been measured to be r(PFS) = 0.38 ± 0.01 and r(GMA) = 0.89 ± 0.01 in free radical polymerization. Variation of the copolymer composition allowed precise control over the refractive index measured at 589, 633, 1320, and 1550 nm. These amorphous copolymers were photo-cross-linked by contact printing and developed by wet etching to produce high quality ridge waveguides with very smooth top surfaces. Low loss single-mode (SM) waveguides exhibit averaged losses over eight ch...

A novel method of preparing thermally stable thin films with intrinsic second-order nonlinear optical activity is described. Design and synthesis yielded new ferroelectric bifunctional liquid crystalline acrylate monomer mixtures with a fast electro-optical response in the chiral smectic C (SmC*) phase. The ferroelectric liquid crystalline monomer mixtures were poled and subsequently cross-linked by in-situ photopolymerization in the surface-stabilized ferroelectric liquid crystal state. After cross-linking the polarization is no longer reversible, hence the material is pyroelectric and not ferroelectric. The cross-linked pyroelectric materials displayed a thermally stable nonlinear optical response.

Hyperbranched, aliphatic polyesters of theoretically calculated molar masses 1200-44 300 were synthesized in the molten state from 2,2-bis(hydroxymethyl)propionic acid (repeating unit of AB(x) type ...

Etude par DSC et microscopie optique de 2 polymeres a base de bis(hydroxy-4 phenoxy) p-xylene et comportant un groupe espaceur respectivement 9 et 11 methylene. La transition est controlee par nucleation et suit l'equation generale d'Aurami. Un processus de rearrangement de la mesophase smectique sans nucleation et suivant l'equation d'Aurami est aussi observe

Nouvelle technique de traitement de surface des polymeres: depot base sur la polymerisation du titre; l'echantillon en masse est dope avec une petite quantite de photosensibilisant cationique, soluble; l'exposition a la lumiere UV cree une surface fortement acide due a la radiolyse du photosensibilisant; l'echantillon est ensuite expose a un monomere adequat, en solution ou en phase gazeuse

Synthese a partir du xylene et de dibromoalcane par synthese de williamsoc avec transfert de phase