Search results for "Chain-growth polymerization"

Preparation of Hyperbranched Polyacrylates by Atom Transfer Radical Polymerization. 2. Kinetics and Mechanism of Chain Growth for the Self-Condensing…

1997

The self-condensing vinyl polymerization (SCVP) of 2-((2-bromopropionyl)oxy)ethyl acrylate (BPEA) has resulted in the formation of hyperbranched polyacrylates. The polymerization mechanism used to polymerize the BPEA was atom transfer radical polymerization (ATRP), a “living”/controlled radical polymerization. This paper details the study of the kinetics of polymerization and the growth of the macromolecule during the polymerization. The results obtained in the polymerization were compared to the theoretical predictions for SCVP. It was determined that the polymerization deviated from the ideal case, as a consequence of the establishment of a dynamic equilibrium in ATRP resulting in the add…

Polymerization of 3-alkylthiophenes with FeCl3

1992

We report on the mechanism of direct oxidation of 3-alkylthiophenes using ferric chloride (FeCl3) as the polymerization oxidant/catalyst to produce high molecular weight poly(3-alkylthiophenes) (P3ATs), conjugated polymers that have potential as electrically and optically active polymers. This study shows that the FeCl3 must exist in the solid state in the reaction mixture to be active as an oxidant in the polymerization of P3AT. A feasible polymerization mechanism for 3-alkylthiophene was developed on the basis of the crystal structure of FeCl3 and quantum chemical computations of thiophene derivatives. The polymerization is hypothesized to proceed through a radical mechanism rather than a…

Effect of hydrogen on the ethylene polymerization process over Ziegler-Natta catalysts supported on MgCl2(THF)2. II. Kinetic studies

2000

This article reports on a study of the effects of hydrogen on the activity of vanadium and titanium catalysts supported on MgCl 2 (THF) 2 in ethylene polymerization. It was found that hydrogen did not change the stable nature of the active sites and the polydispersity index of the polyethylene obtained. The propagation rate, expressed as k p , was found to be independent of the presence and concentration of hydrogen, indicating that this reacting agent does not modify the reactivity of the active sites. However, the presence of hydrogen in the polymerization medium is responsible for partial deactivation of the active sites just before polymerization is initiated.

Peculiar behavior of degenerative chain transfer polymerization of a phosphonated methacrylate

2009

Living/controlled radical polymerization of dimethyl(methacryloyloxy)methyl phosphonate (MAPC) has been attempted using degenerative transfer to produce block copolymers. RAFT polymerization of this monomer is sensitive to very low level of oxygen and in any case limited to low monomer conversion. Reverse iodine transfer polymerization (RITP) leads to higher monomer conversion with a limited amount of living polymer (55% by H NMR), precluding an efficient synthesis of block copolymers. A PMMA-b-PMAPC diblock copolymer was therefore synthesized by iodine transfer polymerization (ITP) of MAPC from a PMMA-Imacro-chain transfer agent prepared by RITP. The diblock copolymer, purified by selectiv…

1987

Synthesis of Defined Poly(silsesquioxane)s: Fast Polycondensation of Trialkoxysilanes in a Continuous-Flow Microreactor

2009

The polycondensation of trialkoxysilanes to PSSQs in a microreactor setup is demonstrated. While continuous-flow processes involving microreactors found various applications in chain growth polymerization, their influence on step-growth polymerization is less explored, and the polycondensation of multifunctional monomers has not been studied in detail. We found significantly increased yields and a decreased polydispersity of the obtained polymers in comparison to the batch process. By variation of the residence time molecular weights could be adjusted reproducibly ranging from M n =1900 to 11000 g · mol -1 . Thus, the microreactor setup offers for the first time the possibility to synthesiz…

Ring opening polymerization of $\varepsilon$-caprolactone in the presence of wet $\beta$-cyclodextrin: Effect of the operative pressure and of water …

2016

International audience; The ring opening polymerization (ROP) of $\varepsilon$-caprolactone (CL) in the presence of $\beta$-cyclodextrin ($\beta$-CD) wasperformed in batch reactors both at room pressure and with the reaction system pressurized with CO$_2$, N$_2$ orAr. Significant enhancements of the polymerization rate was observed when the ROP was carried out withwet $\beta$-CD under pressure. For example, after 24 hours at 120° C with a $\beta$-CD/CL molar ratio of about1/100, the monomer conversion increased from 4 to 98–99% when the pressure was changed from 0.1to 12.5–13.0 MPa independent of the nature of the compressing gas. MALDI-TOF analyses indicated thata major fraction of polymer…

Polyreactions in ordered systems: Polymerization of octadecyl methacrylate in monolayers at the gas–water interface

1977

The ultraviolet-initiated polymerization of octadecyl methacrylate (ODMA, octadecyl 2-methyl-2-propenoate) as a monomolecular layer at the gas-water interface was studied. The polymerization was carried out at 27°C at the nitrogen-water interface; air inhibits the polymerization. At 27°C the ODMA monolayer exhibits three different states which were characterized by surface pressure-area diagrams and by surface potential measurements. The ODMA monolayer was polymerized under constant surface pressure in the range between 0 and 10 dyne/cm. The polymerization was followed by recording the contraction of the film. The conversion was determined by comparison of the area per monomer unit during p…

The role of dislocations in the solid-state polymerization of monomers having conjugated triple bonds: A study of 2,4-hexadiyne-1,6-diol bis(p-toluen…

1975

The crystal structure of the monomer bis(p-toluene sulfonate) ester of 2,4-hexadiyne-1,6-diol (pT) is conducive from the viewpoint of both the separation distances and molecular configuration, to polymerization, irrespective of whether initiation is thermal, photochemical, or mechanical. The dislocations present in the monomer and polymer structures have been characterized by employing optical microscopic techniques. The slip system (102)[010] is found to be present in both monomer and polymer crystals but the (010)[001] system is found only in the monomer. On this basis a crystal structure for the monomer is proposed based on existing crystallographic information relating to the structure …

Synthesis of well-defined polymeric activated esters

2008

Monomers bearing an activated ester group can be polymerized under various controlled polymerization techniques, such as ATRP, NMP, RAFT polymerization, or ROMP. Combining the functionalization of polymers via polymeric activated esters with these controlled polymerization techniques generate possibilities to realize highly functionalized polymer architectures. Within this highlight two different research areas of activated esters in polymer science will be discussed: (i) the preparation of defined reactive polymer architectures by controlled polymerization techniques and (ii) the preparation of defined reactive thin films. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6…