Search results for "Polymers"
showing 10 items of 3567 documents
Step-growth Polymerization ofBistriazolinediones with1,1-Diphenylethylene
1996
The reactions of 4-ethyl-1,2,4-triazoline-3,5-dione (ETD) (1) and 4-phenyl-1,2,4-triazoline-3,5-dione (PhTD) (2) with 1,1-diphenylethylene (DPE) (3) were investigated at room temperature. The reactions are very fast and are completed in less than 4 min. These reactions lead to the formation of two 2 :1 adducts via double Diels-Alder and Diels-Alder-ene reactions in a ratio of 1.35 : 1. The structure of these adducts where R = Et were determined by X-ray analysis of a single crystal. These compounds were used as models for the polymerization reactions. The reaction of bistriazolinediones (1,6-bis-(3,5-dioxo-1,2,4-triazoline-4-yl)hexane and bis-(p-3,5-dioxo-1,2,4-triazoline-4-ylphenyl)methane…
Cyclodextrins in Polymer Synthesis: Enantiodiscrimination in Free-Radical Polymerization of Cyclodextrin-Complexed Racemic N -Methacryloyl-D,L -pheny…
2003
The enantiodiscriminating polymerization of racemic cyclodextrin-complexed N-methacryloylphenylalanine methyl ester is investigated 1 H NMR spectra of the complexes with methylated β-cyclodextrin in D 2 O manifest splittings due to chiral recognition. The different stabilities of the diastereomeric complexes influence the kinetics of the homopolymerization, particularly at 0°C. An enrichment of the residual N-methacryloyl-L-phenylalanine methyl ester of 14% was achieved after 21 h of polymerization.
NMR and Quantum-Chemical Study on the Structure of Ester Enolate−Aluminum Alkyl Complexes as Models of the Active Center in the Anionic Polymerizatio…
1999
6Li and 13C NMR on ethyl α-lithioisobutyrate (EiBLi) and quantum-chemical (DFT) calculations on methyl α-lithioisobutyrate (MiBLi) were used to elucidate the structure of the active center in the anionic polymerization of methacrylates in the presence of triethylaluminum (AlEt3) in toluene. This study reveals ester enolate/aluminum alkyl complexes with different degrees of association, (MiBLi·AlEt3)n (n = 1, 2, 4), and different stoichiometries, MiBLi·xAlEt3 (x = 1, 2). In the presence of methyl pivalate (MPiv), which is taken as a model compound for the monomer and polymer, complexes such as (MiBLi·MPiv·AlEt3)n (n = 1, 2) are formed. These complexes can dissociate into MiBLi·2AlEt3 and MPi…
Polymerization of ε-caprolactone using heterobimetallic lanthanocene complexes
1997
The chiral heterobimetallic complexes Li[Ln(η 5 :η 1 -C 5 R 4 1 SiMe 2 NCH 2 CH 2 R 2 ) 2 ] (ln= Y, Lu; C 5 R 4 1 = C 5 Me 4 , C 5 H 4 , 3-C 5 H 3 tBu; R 2 = OMe, NMe 2 ) have been found to polymerize e-caprolactone to give a polymer of high molecular weight (M n > 20000) and moderate polydispersity (M w /M n < 2). Failure to observe a correlation between monomer/initiator ratio and molecular weight suggest a polymerization mechanism different from a pseudo-anionic mechanism
Cyclodextrins in Polymer Synthesis: Free Radical Polymerization of a N-Methacryloyl-11-aminoundecanoic Acid/β-Cyclodextrin Pseudorotaxane in an Aque…
1999
The relatively hydrophobic monomer N-methacryloyl-11-aminoundecanoic acid (1) was incorporated as a guest into the cavity of β-cyclodextrin (β-CD) as a host, yielding the water-soluble monomer N-me...
Cylindrical Brush Polymers with Polysarcosine Side Chains: A Novel Biocompatible Carrier for Biomedical Applications
2015
Cylindrical brush polymers constitute promising polymeric drug delivery systems (nanoDDS). Because of the densely grafted side chains such structures may intrinsically exhibit little protein adsorption (“stealth” effect) while providing a large number of functional groups accessible for bioconjugation reactions. Polysarcosine (PSar) is a highly water-soluble, nonionic and nonimmunogenic polypeptoid based on the endogenous amino acid sarcosine (N-methyl glycine). Here we report on the synthesis, characterization and biocompatibility of cylindrical brush polymers with either polysarcosine side chains or poly-l-lysine-b-polysarcosine side chains. The latter leads to block copolypept(o)id based…
Introducing PeptoPlexes: Polylysine-block-Polysarcosine Based Polyplexes for Transfection of HEK 293T Cells
2014
A series of well-defined polypeptide-polypeptoid block copolymers based on the body's own amino acids sarcosine and lysine are prepared by ring opening polymerization of N-carboxyanhydrides. Block lengths were varied between 200-300 for the shielding polysarcosine block and 20-70 for the complexing polylysine block. Dispersity indexes ranged from 1.05 to 1.18. Polylysine is polymerized with benzyloxycarbonyl as well as trifluoroacetyl protecting groups at the ϵ-amine group and optimized deprotection protocols for both groups are reported. The obtained block ionomers are used to complex pDNA resulting in the formation of polyplexes (PeptoPlexes). The PeptoPlexes can be successfully applied i…
Polysarcosine-containing copolymers: Synthesis, characterization, self-assembly, and applications
2018
Although the first polysarcosine (pSar) synthesis by Wesseley et al. was reported almost a century ago, it was only recently that pSar gained broader attention and is considered a potential alternative of poly(ethylene glycol) (PEG). In contrast to polyethers, such as PEG, pSar is a polypeptoid based on the amino acid sarcosine, i.e. N-methylated glycine. As a polymer, pSar combines PEG-like properties, e.g., excellent solubility in water, protein resistance, low cellular toxicity and a non-immunogenic character, while being based on endogenous material. Sarcosine can be obtained in a simple one-step reaction of bromoacetic acid and methylamine, easily transferred into the sarcosine N-(thio…
Synthesis and characterization of bisalkylated polysarcosine-based lipopolymers
2019
The use of PEGylated lipids for the synthesis of stealth liposomes and lipid formulations for nucleic acid delivery has promoted the development of nanoparticle based drugs for cancer therapy, and chronic diseases. Moreover, several other nanomedicines based on these materials have advanced into clinical trails. This enormous success, however, has recently been compromised by the occurrence of immune responses towards PEG, which render pharmacokinetics and can substantially reduce the therapeutic efficiency of drugs. Therefore, alternatives for PEGylated lipids with comparable or even identical solution properties are required. In this work, we report the synthesis of polysarcosine based li…
Universal glue for cells
2012
A dendritic polymer consisting of inversely oriented lipid head groups on a polyvalent polyglycerol scaffold makes an effective reversible biomembrane adhesive that may find use as a tissue sealant and a drug-delivery vehicle.