Search results for "opening"

Phenoxyamidine Zn and Al Complexes: Synthesis, Characterization, and Use in the Ring-Opening Polymerization of Lactide

2019

International audience; Herein we report the synthesis of new ditopic ligands, which consist of a phenoxy group and N,N,N'trisubstituted amidines linked by a methylene spacer (L1-L4). Their coordination chemistry has been studied/investigated with Zn(II) and Al(III). Alkane elimination route between the phenol-amidine proligands (L1H-L4H) and Et2Zn led to dinuclear complexes [(L1-L4)ZnEt]2 (1a-4a) in which the Zn centers are chelated by phenoxyamidine ligands and bridged through the oxygen atom of the phenoxy groups. Salt metathesis reaction between two equivalents of the sodium amidine phenate L1Na and ZnCl2 led to a bis-chelate chiral spiro-complex (L12Zn) 1a'. Analogous alkane eliminatio…

A head-to-head comparison of poly(sarcosine) and poly(ethylene glycol) in peptidic, amphiphilic block copolymers

2015

Abstract In this work we compare chemical and solution properties, like critical aggregate concentrations (CAC) and hydrodynamic radii of aggregates based on either poly(ethylene glycol) or poly(sarcosine) block copolymers in aqueous solution. The amine functionalized, hydrophilic polymers poly(sarcosine) (degree of polymerization, X n  = 100 and 200) and PEG (X n  = 121 and 242) of comparable hydrodynamic volume were used to initiate the ring opening polymerization of α-amino acid- N -carboxyanhydrides based on ɣ-benzyl- l -glutamate (Glu(OBn)) or e-carboxybenzyl- l -lysine (Lys(Z)). The second, hydrophobic block was kept at a degree of polymerization of 25 and 50 to enable a direct compar…

Inguinal Hernia: Defect Obliteration with the 3D Dynamic Regenerative Scaffold Proflor™.

2021

Prosthetic inguinal hernia repair presents significant challenges. Some of these, such as mesh fixation and quality of the biologic response, are still debated among surgeons. For example, there is no strong consensus regarding a specific condition that characterizes the surgical procedure during herniorrhaphy. This issue concerns management of the hernia defect, which in conventional hernia repair with flat meshes remains patent. However, a critical analysis of typical postoperative complications after inguinal hernia repair reveals that some of these adverse events are related to patency of the hernial opening. Postoperative discomfort, pain with specific movements and even hernia recurre…

Ring opening polymerization of ε-caprolactone initiated by titanium and vanadium complexes of ONO-type schiff base ligand

2021

AbstractA phenoxy-imine proligand with the additional OH donor group, 4,6-tBu2-2-(2-CH2(OH)-C6H4N = CH)C6H3OH (LH2), was synthesized and used to prepare group 4 and 5 complexes by reacting with Ti(OiPr)4 (LTi) and VO(OiPr)3 (LV). All new compounds were characterized by the FTIR, 1H and 13C NMR spectroscopy and LTi by the single-crystal X-ray diffraction analysis. The complexes were used as catalysts in the ring opening polymerization of ε-caprolactone. The influence of monomer/transition metal molar ratio, reaction time, polymerization temperature as well as complex type was investigated in detail. The complexes showed high (LTi) and moderate (LV) activity in ε-caprolactone polymerization a…

Ring opening polymerization of cyclic esters with metal free catalysts

2012

Promotion of Social Policies – an Investment in the Future: Canada – European Union – Baltic States – Nordic Countries

2009

This volume represents presentations, discussions and research papers in conjunction with the Forum for a Comparative Dialog- an Investment in the Future. The Forum was held in Riga at the University of Latvia on November 6-8, 2008 and was organised by the Centre for European and Transition Studies at the University of Latvia and Capilano University, Canada.

Rethinking Cysteine Protective Groups:S-Alkylsulfonyl-l-Cysteines for Chemoselective Disulfide Formation

2016

The ability to reversibly cross-link proteins and peptides grants the amino acid cysteine its unique role in nature as well as in peptide chemistry. We report a novel class of S-alkylsulfonyl-l-cysteines and N-carboxy anhydrides (NCA) thereof for peptide synthesis. The S-alkylsulfonyl group is stable against amines and thus enables its use under Fmoc chemistry conditions and the controlled polymerization of the corresponding NCAs yielding well-defined homo- as well as block co-polymers. Yet, thiols react immediately with the S-alkylsulfonyl group forming asymmetric disulfides. Therefore, we introduce the first reactive cysteine derivative for efficient and chemoselective disulfide formation…

Crack growth analysis at adhesive–adherent interface in bonded joints under mixed mode I/II

2008

The propagation of an interface crack subjected to mixed mode I/II was investigated for two 2024-T351 aluminum thin layers joined by means of DP760 epoxy adhesive produced by 3M©. On the basis of beam theory, an analytical expression for computing the energy release rate is presented for the mixed-mode end loaded split (MMELS) test. The analytical strain energy release rate was compared by finite element (FE) analysis using the virtual crack closure technique (VCCT). Several fatigue crack growth tests were carried out in a plane bending machine to compare the experimental energy release rates to those of the analytical and FE solutions. Experimental results showed the relationship between t…

A controlled and versatile NCA polymerization method for the synthesis of polypeptides

2013

A versatile and simple methodology for the preparation of well-defined polyglutamate nanocarriers is described. For the first time ammonium salts with non-nucleophilic tetrafluoroborate anions are used as initiators for the ring opening polymerization of alpha-N-carboxyanhydrides (NCAs) allowing a multigram scale polyglutamate synthesis with defined molecular weight (up to 800 units), low polydispersity (<1.2), controlled chain end functionality and adequate stereoselectivity and absence of any trace of toxic impurity to allow biomedical applications.

L'ecomuseo del grano e del pane: un percorso progettuale centrato sul design

2018

La festa di S. Giuseppe, oltre che un’importante e sentita ricorrenza religiosa, è a Salemi soprattutto la “festa dei pani”; bellissime realizzazioni di alto artigianato artistico, la cui sapienza si tramanda nelle famiglie e nelle associazioni di donne che per mesi lavorano alla produzione dell’enorme quantità delle piccole e grandi forme di pane, per rivestire le costruzioni votive che accolgono il rito della cena. Nasce quindi l’idea di proporre un “Ecomuseo del grano e del pane” nel Collegio dei Gesuiti, valorizzando e riaprendo al pubblico uno spazio di grande interesse storico-architettonico. Nell’ambito della consolidata collaborazione del Comune di Salemi con il Dipartimento di Arch…