Search results for "Macromonomer"
showing 10 items of 32 documents
Synthesis strategies and properties of smart amphiphilic networks
1996
This paper briefly surveys recent developments in the field of amphiphilic networks (APN) which are a new class of crosslinked polymer systems consisting of covalently bonded hydrophobic and hydrophilic chain segments. The covalent bonds between immiscible hydrophobic and hydrophilic polymer chains prevent demixing and yield polymer networks with unique structure and properties. Telechelic macromonomers provide the basis for the first generation of APNs obtained by copolymerization of the macromonomer with selected low molecular weight monomers. Synthesis of a variety of APNs using methacrylate-telechelic polyisobutylene (PIB) macromonomers prepared by living carbocationic polymerization (L…
Copolymerization of methacryloyl-terminated PMMA macromonomers with methyl methacrylate
1992
Methacryloyl-terminated macromonomers (MM) of polymethylmethacrylate (PMMA) of two different molecular weights were prepared by group transfer polymerization (GTP). They were copolymerized with methyl methacrylate (MMA) by radical polymerization using toluene as the solvent. The relative reactivity of the MM, 1/r1, decreases with increasing initial MM concentration. This is interpreted as a consequence of the increasing viscosity of the reaction medium leading to an increasing diffusion control of the MM addition. At a constant weight ratio of MMA to MM the reactivity of the longer macromonomer is higher than of the shorter one. Increasing the molar ratio [MMA]/[MM], i.e. increasing the ave…
Synthesis and large scale fractionation of non-linear polymers: brushes and hyperbranched polymers
2002
Polymer brushes with poly(methyl methacrylate) (PMMA) backbone and polystyrene side chains were synthesized by radical polymerization of ω-methacryloyl-polystyrene macromonomers. Hyperbranched PMMA was obtained by means of self-condensing group transfer copolymerization of methyl methacrylate with an initiator-monomer containing a polymerizable methacryloyl moiety and an initiating silylketeneacetal function. Both non-linear products were fractionated using the method of continuous polymer fractionation, consisting in a particular type of continuous countercurrent extraction. The combination of methyl ethyl ketone (solvent) with acetone (AC) (precipitant) turned out to be suitable for the f…
Efficient Synthesis of High Molar Mass, First- to Fourth-Generation Distributed Dendronized Polymers by the Macromonomer Approach
2003
A homologous series of first- to fourth-generation (G1±G4) dendronized macromonomers, 5, 7, 10, and 12, was synthesized, and their poly- merization behavior under radical con- ditions investigated. These conditions were thermally induced radical poly- merization (TRP) and atom-transfer radical poymerization (ATRP). TRP was applied to all monomers and gave polymers PG1±PG4, whose molar masses range from several millions for PG1 to estimated several hundreds of thousands for PG2 and PG3, and to the oligomeric regime for PG4. ATRP was applied only to the G1 and G2 monomers 5 and 7. Kinetic studies on monomer 5 provide evidence that its polymerization proceeds in a control- led fashion. The hig…
Collapse of Cylindrical Brushes with 2-Isopropyloxazoline Side Chains Close to the Phase Boundary
2013
A high-molar-mass cylindrical brush polymer with a main chain degree of polymerization of Pw = 1047 is synthesized by free-radical polymerization of a poly-2-isopropyloxazoline macromonomer with Pn = 28. The polymerization is conducted above the lower phase transition temperature of the macromonomer, i.e., in the phase-separated regime, which provides a sufficiently concentrated macromonomer phase mandatory to obtain high-molar-mass cylindrical brushes. Upon heating to the phase transition temperature, the hydrodynamic radius is observed to shrink from 34 to 27 nm. Further increase in temperature resulted in aggregated chains which were observed to coexist with single chains until eventuall…
A Facile Two-Step Route to Branched Polyisoprenes via ABn-Macromonomers
2007
A facile two-step synthesis for branched poly(isoprene)s (PI) based on polyaddition of AB n -type macromonomers is described. The synthesis of the macromonomers was achieved by anionic polymerization of isoprene and subsequent end-capping of the polymers by addition of chlorodimethylsilane to the living carbanions. This led to PI-based macromonomers with narrow polydispersity (M w /M n < 1.15) and molecular weights in the range of 1700 -22100 g mol -1 . Synthesis of the branched polymers was carried out by a hydrosilylation-based polymerization of the macromonomers. Characterization via SEC, SEC-MALLS, coupled SEC-viscosimetry and 1 H-NMR-spectroscopy supported the formation of branched str…
Ion-Induced Stretching of Low Generation Dendronized Polymers with Crown Ether Branching Units
2009
Synthesis of the first (G1) and second generation (G2) dendronized macromonomers MG1 and MG2 with the dibenzo-24-crown-8 moiety as branching unit is reported. The corresponding dendronized polymers, the polymethacrylates PG1 and PG2, were synthesized by free radical polymerization using AIBN as initiator at 60−80 °C. Static and dynamic light scattering revealed a significant chain expansion upon complexation of these polymers’ crown ether side chains with K+ ions. It is concluded that electrostatic repulsion does not significantly contribute to the chain expansion because of excessive counterion binding even well below the Manning limit, as evidenced by 19F NMR and 1H−19F NOE experiments. R…
Ferrocenyl-functionalized long chain branched polydienes
2009
A convenient two-step approach for the synthesis of ferrocenyl-functionalized long chain branched polydienes, based on both butadiene and isoprene, respectively, is presented. Classical living anionic polymerization was used to synthesize different AB n type poly(diene) macromonomers with moderate molecular weights between 1700 and 3200 g/mol and narrow polydispersity. Quantitative end-capping with chlorodimethylsilane resulted in the desired AB n macromonomer structures. In the ensuing Pt-catalyzed hydrosilylation polyaddition, branched, functionalized polydienes were obtained by a concurrent AB n + AR type of copolymerization with mono-and difunctional ferrocenyl silanes (fcSiMe 2 H or fc…
A green route to synthesize poly(lactic acid)-based macromonomers in scCO2 for biodegradable nanoparticle production
2014
Poly(lactic acid)-based macromonomers, aimed at biomedical applications and with well-defined average chain length, are produced through catalytic ring-opening polymerization of L,L-lactide co-initiated by a co-monomer bearing a double bond. Reactions have been carried out in supercritical carbon dioxide (scCO2) at different temperatures, ranging from 90 to 130 °C. The resulting oligomers have been characterized by different techniques (1H-NMR, 13CNMR, MALDI-TOF, ESI, GPC, FT-IR, TGA), which show that oligomers with narrower molecular weight distribution are produced at the lowest temperature. In addition, a significant reduction of the impact of the secondary reactions has been found at th…
Acrylic Graft Copolymers Via Macromonomers
1995
Comb-shaped poly(methyl methacrylate) (PMMA) and PMMA grafted with poly(nbutyl acrylate) (PnBuA) were prepared by radical copolymerisation of ω-methacryloyl-PMMA with MMA and nBuA, respectively. The comb-shaped PMMA is characterised with respect to radius of gyration by using GPC equipped with a multi-angle laser light scattering detector. The radical copolymerisation of the macromonomer with nBuA in toluene follows complex kinetics. The dependence of the relative reactivity of the macromonomer on absolute concentration and on the ratio of comonomers may be explained by preferential solvation of comonomers by segments of their own kind (“bootstrap effect”) or even micelle formation. However…