Search results for "Acrylate"

Short and Efficient Chemoenzymatic Synthesis of Goniothalamin.

2004

A high-yielding three-step synthesis of goniothalamin involving an enzymatic kinetic resolution in the presence of vinyl acrylate followed by ring-closing metathesis is discussed.

Multi-Arm Star Polyglycerol-block-poly(tert-butyl acrylate) and the Respective Multi-Arm Poly(acrylic acid) Stars

2006

Well-defined multi-arm star block copolymers, polyglycerol-block-poly(tert-butyl acrylate) (PG-b-PtBA), with average arm-numbers of 17, 27, 36, 66 and 90 arms, respectively, have been prepared by atom transfer radical polymerization (ATRP) of tBA in acetone, using a core-first strategy. After hydrolysis with excess concentrated HCl in refluxing dioxane, full hydrolysis of the tert-butyl ester groups was achieved, resulting in multi-arm star polyelectrolytes, polyglycerol-block-poly(acrylic acid) (PG-b-PAA). The hyperbranched macroinitiators employed were prepared on the basis of hyperbranched polyglycerols via esterification with 2-bromoisobutyryl bromide. Both CuBr/PMDETA and CuBr/Me 6 TRE…

Copolymerization of n-Butyl Acrylate with Methyl Methacrylate and PMMA Macromonomers:  Comparison of Reactivity Ratios in Conventional and Atom Trans…

1999

The reactivity ratios of n-butyl acrylate (nBuA) with methyl methacrylate (MMA) and ω-methacryloyl-PMMA macromonomers (MM) in conventional and atom transfer radical copolymerization (ATRP) have been determined. For the copolymerization of nBuA with MMA, good agreement of the ratios is observed between conventional and controlled radical copolymerization, indicating that chemoselectivities in both processes are similar. The relative reactivity of the MM (1/rnBuA) in conventional copolymerization is significantly lower than that of MMA. It depends on the concentration of the comonomers but is not significantly influenced by the length of the MM. At high concentrations the relative reactivity …

Mechanism of Anionic Polymerization of (Meth)acrylates in the Presence of Aluminum Alkyls, 6. Polymerization of Primary and Tertiary Acrylates

1998

The kinetics of the polymerization of n-butyl acrylate initiated by lithiated ester enolates in the presence of aluminum alkyls was investigated in toluene and in toluene/Lewis base mixed solvents at −78 °C. In pure toluene, curved time−conversion plots, incomplete monomer conversion, and broad molecular weight distributions (Mw/Mn ≈ 2) are observedin the absence of aluminum alkyls the molecular weight distributions are significantly broader (Mw/Mn > 14). High monomer conversions and narrower molecular weight distributions (Mw/Mn ≈ 1.5) are obtained when using Lewis bases (e.g., methyl pivalate) as cosolvents. The polymerization of tert-butyl acrylate rapidly reaches full monomer conversion…

Kinetics and mechanism of group transfer polymerization of N-butyl acrylate catalyzed by Hgl2 /(CH3 )3 Sil in toluene

1994

The group transfer polymerization (GTP) of n-butyl acrylate (nBuA) using 1-methoxy-1-(trimethylsiloxy)-2-methyl-1-propene (MTS) as an initiator, mercuric iodide (HgI2) as a catalyst in toluene at room temperature gives a very good control of molecular weight and narrow molecular weight distribution. (Mw/Mn < 1.2). Kinetic studies in this system reveal that this reaction is rather slow, half-lives being in the range of hours. The kinetic order of the apparent rate constant of propagation with respect to initiator and catalyst concentrations were found to be near to unity. However, the first-order time-conversion plots exhibit considerable induction periods. Upon addition of trimethylsilyl io…

Synthesis and solution properties of star-shaped poly(tert-butyl acrylate)

2000

A series of star polymers consisting of poly(tert-butyl acrylate) arms and an ethyleneglycol dimethacrylate (EGDMA) microgel core were synthesized using anionic polymerization. The effect of various parameters (precursor length, ratio [[EGDMA]/[Initiator], reaction time, and overall concentrations) on the average number of arms was investigated. Molecular weights were determined using GPC coupled with an online viscometer and MALLS. The exponents for the relation between intrinsic viscosity or radius of gyration and molecular weight, respectively, are extremely low, indicating that the dimensions of the star polymers only slightly increase with the number of arms. After a certain number of …

1993

The influence of lithium tert-butoxide (tBuOLi) and of lithium chloride on the oligomerization of tert-butyl acrylate (tBuA) initiated by tert-butyl α-lithioisobutyrate (tBiB-Li) was investigated. These additives affect both the kinetics and the product distribution. Whereas the addition of LiCl leads to a narrower molecular-weight distribution (MWD) the presence of tBuOLi induces broader MWD's, characterized by a very high fraction of the dimer. Both additives decrease the rates of propagation to different degrees. These effects are discussed on the basis of the formation of aggregates and adducts, the lithiated dimer having a higher tendency to form aggregates than the other oligomers. Th…

1976

Die Herstellung einer molekulareinheitlichen Tri-, Tetra- und Pentamethacrylsäure. V. Mitt. Modelle für Matrizenreaktionen

1968

Vom p-Kresol sowie einer phenolischen Zwei- und einer Dreikernverbindung wurden mit verschiedenen Acylierungsmethoden Methacrylsaureester erhalten; die Zweikernverbindung enthielt danach zwei und die Dreikernverbindung drei Methacrylreste. Loste man diese Methacrylsuureester in groser Verdunnung in siedendem Benzol und lies gleichzeitig einen grosen Uberschus an Radikalen aus α.α′-Azoisobuttersauredinitril einwirken, so wurde beim Methacrylsaure-p-kresylester eine Polymerisation unterdruckt. Bei den mehrfachen Estern der Mehrkernverbindungen wurde die polyrmerisationsahnliche Additionsreaktion auf die einzelnen Molekule begrenzt (intramolckulare Polymerisation); sie ergab neben einer cyclis…

Magnetic molecularly imprinted polymers for the selective determination of cocaine by ion mobility spectrometry

2018

Abstract Magnetic molecularly imprinted polymers (MMIPs) were prepared for cocaine recognition by bulk polymerization in the presence of magnetic nanoparticles (MNPs). Two reagents (polyethylene glycol (PEG) and 3-(trimethoxysilyl)propyl methacrylate (V)) were used for MNPs modification. MMIPs were characterized and compared in terms of loading capacity, reusability, accuracy and precision for the extraction of cocaine from saliva samples. It was observed that V-MMIPs gave higher physical stability than PEG-MMIPs. Thus, V-MMIP were used for the analysis of cocaine users saliva. The developed procedure based on ion mobility spectrometry (IMS) provided limits of detection and quantification o…