scholarly journals A Novel Strategy for the Synthesis of Amphiphilic and Thermoresponsive Poly(N-isopropylacrylamide)-b-Polystyrene Block Copolymers via ATRP

Polymers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1484 ◽  
Author(s):  
Magdalena Fedorczyk ◽  
Anna Krzywicka ◽  
Piotr Cieciórski ◽  
Jan Romański ◽  
Elżbieta Megiel
Keyword(s):  
Block Copolymers ◽  
Polymer Chains ◽  
Size Exclusion ◽  
Synthetic Approach ◽  
Scanning Calorimetry ◽  
Styrene Polymerization ◽  
Exclusion Chromatography ◽  
Arget Atrp ◽  
Novel Strategy ◽  
Two Stages

A new synthetic approach is presented for the preparation of Poly(N-isopropylacrylamide-block-styrene) PNIPAM-b-PS via an Atom Transfer Radical Polymerization (ATRP) technique. The proposed method is based on application of 2-chloro-N-(2-hydroxyethyl)propanamide (NCPAE) as a bifunctional initiator, which enables ATRP of two monomers, differing in activity and polarity, into two stages. The synthesized copolymer molecules contain two well-defined polymer chains connected by a linker, which is a derivative of the proposed initiator. Using NCPAE led to PNIPAMs with well-planned molecular weight, low polydispersities (PDI=1.1÷1.3) and hydroxyl functionality. Activation of such blocks for initiation of styrene polymerization was performed using α-bromoisobutyryl bromide. After such a modification, the synthesized homopolymers acted as macroinitiators in ARGET ATRP and a well-defined polystyrene block, as the next one in the polymer chain was successfully formed. Both of the synthesized macromolecules, PNIPAM and PNIPAM-b-PS, exhibit a thermoresponsive behavior with explicit lower critical solution temperatures (LCST) in their aqueous solutions. The synthesized homopolymers and subsequently derived block copolymers were characterized using Size-Exclusion Chromatography, Differential Scanning Calorimetry, Dynamic Light Scattering, and NMR spectroscopy.

A study on the kinetics and thermal properties of polystyrene/diatomite nanocomposites prepared via in situ ATRP

2018 ◽  
Vol 33 (2) ◽  
pp. 180-197 ◽  
Author(s):  
Khezrollah Khezri ◽  
Yousef Fazli
Keyword(s):  
Molecular Weight ◽  
In Situ Polymerization ◽  
Structural Characteristics ◽  
Nitrogen Adsorption ◽  
Linear Increase ◽  
Size Exclusion ◽  
Scanning Calorimetry ◽  
Morphological Studies ◽  
Exclusion Chromatography

Pristine mesoporous diatomite was employed to prepare polystyrene/diatomite composites. Diatomite platelets were used for in situ polymerization of styrene by atom transfer radical polymerization to synthesize tailor-made polystyrene nanocomposites. X-Ray fluorescence spectrometer analysis and thermogravimetric analysis (TGA) were employed for evaluating some inherent properties of pristine diatomite platelets. Nitrogen adsorption/desorption isotherm is applied to examine surface area and structural characteristics of the diatomite platelets. Evaluation of pore size distribution and morphological studies were also performed by scanning and transmission electron microscopy. Conversion and molecular weight determinations were carried out using gas and size exclusion chromatography, respectively. Linear increase of ln ( M0/M) with time for all the samples shows that polymerization proceeds in a living manner. Addition of 3 wt% pristine mesoporous diatomite leads to an increase of conversion from 72% to 89%. Molecular weight of polystyrene chains increases from 11,326 g mol−1 to 14134 g mol−1 with the addition of 3 wt% pristine mesoporous diatomite; however, polydispersity index values increases from 1.13 to 1.38. Increasing thermal stability of the nanocomposites is demonstrated by TGA. Differential scanning calorimetry shows an increase in glass transition temperature from 81.9°C to 87.1°C by adding 3 wt% of mesoporous diatomite platelets.

scholarly journals Homogeneous Distribution of Polymerizable Coumarin Dyes for Active Few Mode POF

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1975
Author(s):  
Florian Jakobs ◽  
Kristoffer Harms ◽  
Jana Kielhorn ◽  
Daniel Zaremba ◽  
Pen Yiao Ang ◽  
...  
Keyword(s):  
Methyl Methacrylate ◽  
Optical Fibers ◽  
High Performance ◽  
Polymer Chains ◽  
Size Exclusion ◽  
Polymerization Process ◽  
Homogeneous Distribution ◽  
Exclusion Chromatography ◽  
Polymer Optical Fibers ◽  
Coumarin Dyes

For most kinds of active polymer optical fibers, a homogeneous distribution of dye molecules over the entire fiber length and cross section is required. In this study, chemical bonding of dyes to poly(methyl methacrylate) (PMMA) by copolymerization is achieved within the polymerization process instead of dissolving the dyes in the monomers. In combination with an improved fabrication mechanism, this leads to homogeneous dye distribution within the preforms. A method for proving the integration of the dyes into the polymer chains has been developed using high-performance liquid chromatography (HPLC) and size exclusion chromatography (SEC). Prestructured core-cladding preforms with dye-doped poly(cylohexyl methacrylate-co-methyl methacrylate)-core have been prepared with the Teflon string technique and were heat-drawn to few mode fibers.

scholarly journals Synthesis and Self-Assembly of Poly(N-Vinylcaprolactam)-b-Poly(ε-Caprolactone) Block Copolymers via the Combination of RAFT/MADIX and Ring-Opening Polymerizations

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1252
Author(s):  
Rodolfo M. Moraes ◽  
Layde T. Carvalho ◽  
Gizelda M. Alves ◽  
Simone F. Medeiros ◽  
Elodie Bourgeat-Lami ◽  
...  
Keyword(s):  
Block Copolymers ◽  
Ring Opening ◽  
Chain Transfer ◽  
Fluorescence Probe ◽  
Size Exclusion ◽  
Proton Nuclear Magnetic Resonance ◽  
Solution Temperature ◽  
Copolymer Composition ◽  
Resonance Spectroscopy ◽  
Scanning Calorimetry

Well-defined amphiphilic, biocompatible and partially biodegradable, thermo-responsive poly(N-vinylcaprolactam)-b-poly(ε-caprolactone) (PNVCL-b-PCL) block copolymers were synthesized by combining reversible addition-fragmentation chain transfer (RAFT) and ring-opening polymerizations (ROP). Poly(N-vinylcaprolactam) containing xanthate and hydroxyl end groups (X–PNVCL–OH) was first synthesized by RAFT/macromolecular design by the interchange of xanthates (RAFT/MADIX) polymerization of NVCL mediated by a chain transfer agent containing a hydroxyl function. The xanthate-end group was then removed from PNVCL by a radical-induced process. Finally, the hydroxyl end-capped PNVCL homopolymer was used as a macroinitiator in the ROP of ε-caprolactone (ε-CL) to obtain PNVCL-b-PCL block copolymers. These (co)polymers were characterized by Size Exclusion Chromatography (SEC), Fourier-Transform Infrared spectroscopy (FTIR), Proton Nuclear Magnetic Resonance spectroscopy (1H NMR), UV–vis and Differential Scanning Calorimetry (DSC) measurements. The critical micelle concentration (CMC) of the block copolymers in aqueous solution measured by the fluorescence probe technique decreased with increasing the length of the hydrophobic block. However, dynamic light scattering (DLS) demonstrated that the size of the micelles increased with increasing the proportion of hydrophobic segments. The morphology observed by cryo-TEM demonstrated that the micelles have a pointed-oval-shape. UV–vis and DLS analyses showed that these block copolymers have a temperature-responsive behavior with a lower critical solution temperature (LCST) that could be tuned by varying the block copolymer composition.

scholarly journals Two-dimensional chromatography of complex polymers. 3. Full analysis of polystyrene-poly(methyl methacrylate) diblock copolymers

e-Polymers ◽  
2002 ◽  
Vol 2 (1) ◽  
Author(s):  
Harald Pasch ◽  
Kibret Mequanint ◽  
Adrian Jörg
Keyword(s):  
Block Copolymers ◽  
Methyl Methacrylate ◽  
Diblock Copolymers ◽  
Size Exclusion ◽  
Molecular Heterogeneity ◽  
Two Dimensional ◽  
Poly Methyl Methacrylate ◽  
Mass Distributions ◽  
Exclusion Chromatography ◽  
Complex Polymers

AbstractPoly(styrene-block-methyl methacrylate)s were fully analyzed by liquid chromatography at the critical point of adsorption (LC-CC) and two-dimensional chromatography. Operating at chromatographic conditions corresponding to the critical points of the homopolymers polystyrene and poly(methyl methacrylate), the block lengths distributions for the different blocks of the block copolymers were determined quantitatively. Information on the amounts and molar mass distributions of homopolymers and coupling products that were identified in the samples as by-products was obtained by on-line coupled 2D chromatography. It was shown that a complete picture of the molecular heterogeneity of block copolymers can be obtained only when information from different chromatographic experiments is combined. Size exclusion chromatography alone is inappropriate for evaluating the molecular heterogeneity of such samples.

Combined Main- and Side-Chain Azobenzene Polyesters: A Potential For Photoinduced Nonlinear Waveguides

1999 ◽  
Vol 561 ◽  
Author(s):  
F. Sahlén ◽  
T. Geisler ◽  
S. Hvilsted ◽  
N. C. R. Holme ◽  
P. S. Ramanujam ◽  
...  
Keyword(s):  
Refractive Index ◽  
Third Harmonic Generation ◽  
Size Exclusion ◽  
Side Chain ◽  
Visible Spectroscopy ◽  
Scanning Calorimetry ◽  
Nonlinear Waveguides ◽  
Third Harmonic ◽  
Exclusion Chromatography ◽  
Uv Visible

ABSTRACTNew combined main- and side-chain azobenzene polyesters, which exhibit an intensity dependent refractive index, have been prepared in order to optically fabricate nonlinear waveguides. Novel sulfone azobenzenes, a diester, (4-[[5-(ethoxycarbonyl)pentyl]sulfonyl]-4'-[[5-(ethoxycarbonyl)pentyl]methylamino] azobenzene, and a diol, 4-[[(8-hydroxy-7-methylhydroxy)-octyl]sulfonyl]-4'-N, N-dimethylamino azobenzene, have been used to prepare new polyesters by transesterification in the molten state. The polyesters have been characterized by UV-visible spectroscopy, differential scanning calorimetry (DSC), size exclusion chromatography (SEC), third harmonic generation (THG) and optical anisotropy measurements. The molar masses of the polyesters were in the range of 5000-10000 g mol−1, which was sufficient in order to spin coat thin films. From THG measurements the polymers are shown to possess an offresonance electronic X(3) of the order 10−12 esu corresponding to a nonlinear refractive index of 2.3×10−14 cm2/W.

RAFT Polymerization of Monomers with Highly Disparate Reactivities: Use of a Single RAFT Agent and the Synthesis of Poly(styrene-block-vinyl acetate)

2013 ◽  
Vol 66 (12) ◽  
pp. 1564 ◽  
Author(s):  
Lily A. Dayter ◽  
Kate A. Murphy ◽  
Devon A. Shipp
Keyword(s):  
Block Copolymers ◽  
Vinyl Acetate ◽  
Chain Transfer ◽  
Raft Polymerization ◽  
Good Control ◽  
Scanning Calorimetry ◽  
Styrene Polymerization ◽  
Reversible Addition ◽  
Raft Agent ◽  
End Group

A single reversible addition–fragmentation chain transfer (RAFT) agent, malonate N,N-diphenyldithiocarbamate (MDP-DTC) is shown to successfully mediate the polymerization of several monomers with greatly differing reactivities in radical/RAFT polymerizations, including both vinyl acetate and styrene. The chain transfer constants (Ctr) for MDP-DTC for both these monomers were evaluated; these were found to be ~2.7 in styrene and ~26 in vinyl acetate, indicating moderate control over styrene polymerization and good control of vinyl acetate polymerization. In particular, the MDP-DTC RAFT agent allowed for the synthesis of block copolymers of these two monomers without the need for protonation/deprotonation switching, as has been previously developed with N-(4-pyridinyl)-N-methyldithiocarbamate RAFT agents, or other end-group transformations. The thermal properties of the block copolymers were studied using differential scanning calorimetry, and those with sufficiently high molecular weight and styrene composition appear to undergo phase separation. Thus, MDP-DTC may be useful for the production of other block copolymers consisting of monomers with highly dissimilar reactivities.

scholarly journals Towards Novel Fluorinated Methacrylic Coatings for Cultural Heritage: A Combined Polymers and Surfaces Chemistry Study

Polymers ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1190 ◽  
Author(s):  
Valentina Sabatini ◽  
Eleonora Pargoletti ◽  
Valeria Comite ◽  
Marco Aldo Ortenzi ◽  
Paola Fermo ◽  
...  
Keyword(s):  
Prolonged Exposure ◽  
Accelerated Aging ◽  
Water Repellency ◽  
Size Exclusion ◽  
Butyl Methacrylate ◽  
Capillary Absorption ◽  
Scanning Calorimetry ◽  
Water Contact ◽  
Coated Materials ◽  
Exclusion Chromatography

In this work, new co- and ter-polymers of methyl methacrylate (MMA), ethyl methacrylate (EMA), and N-butyl methacrylate (nBuMA), containing just 1% mol × mol−1 of a fluorinated co-monomer, 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-octyl methacrylate (POMA), were synthesized. After an UV accelerated aging test, the photo-chemical stability of the polymers prepared was determined by 1H NMR and FT-IR spectroscopy, size exclusion chromatography, differential scanning calorimetry and wettability measurements. The polymers were applied to Botticino tiles to achieve better performances in terms of water repellency and consequently deterioration resistance. One-year prolonged exposure to a real environment was conducted and the properties of the coated materials and their performances were studied using different surface techniques such as water contact angle (WCA) and colorimetric measurements (CIELaB), capillary absorption, permeability (RVP) tests and soluble salts determination. The effectiveness of the fluorinated methacrylic coatings was clearly demonstrated; among all the resins, the co-polymer MMA_POMA seems to be the most performing one. Furthermore, both the UV photo-chemical resistance and the easiness of removal was successfully studied.

Monitoring the chemical heterogeneity of metallocenecatalysed copolymers of ethylene and higher 1-olefins using CRYSTAF and SEC-FTIR

e-Polymers ◽  
2003 ◽  
Vol 3 (1) ◽  
Author(s):  
Sven M. Graef ◽  
Robert Brüll ◽  
Harald Pasch ◽  
Udo M. Wahner
Keyword(s):  
Differential Scanning Calorimetry ◽  
Size Exclusion Chromatography ◽  
Catalyst System ◽  
Size Exclusion ◽  
Side Chain ◽  
Chemical Heterogeneity ◽  
Scanning Calorimetry ◽  
Crystallisation Temperature ◽  
Exclusion Chromatography

Abstract Copolymers of ethylene with 1-decene, 1-tetradecene and 1-octadecene were prepared using the catalyst system racEt[Ind]2ZrCl2/MAO and were analysed with regard to chemical heterogeneity using crystallisation analysis fractionation (CRYSTAF), differential scanning calorimetry (DSC) and size exclusion chromatography coupled to FTIR (SEC-FTIR). The melting and crystallisation temperatures from DSC decrease linearly with increasing amount of comonomer, independently of the nature thereof. The decrease in crystallisation temperature from CRYSTAF of copolymers with higher 1-olefin content indicates a small dependence on the length of the side chain. The chemical heterogeneity of the copolymers as analysed by DSC and CRYSTAF broadens with increasing comonomer concentration.

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