Polycondensation of ‘a − bn’ or ‘a2 + + bn’ Monomers ‐ A Comparison

Kricheldorf, Hans R.

doi:10.1002/marc.200700261

Cited by 37 publications

(40 citation statements)

References 189 publications

(194 reference statements)

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“…Generally, cyclization could be formed through intramolecular and intermolecular reactions . However, based on ESI‐MS, it was exclusively managed to designate the intramolecular reactions (due to side reactions such as intramolecular esterification or etherification reactions) . The representative structures of dimer, trimer and tetramer cyclic structures are illustrated in Scheme .…”

Section: Resultsmentioning

confidence: 99%

Lignin valorization by forming toughened thermally stimulated shape memory copolymeric elastomers: Evaluation of different fractionated industrial lignins

Sivasankarapillai

McDonald

2014

J of Applied Polymer Sci

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Lignin-based thermal responsive dual shape memory copolymeric elastomers were prepared with a highly branched prepolymer (HBP, A 2 B 3 type) via a simple one-pot bulk polycondensation reaction. The effect of fractionated lignin type (with good miscibility in the HBP) on copolymer properties was investigated. The thermal and mechanical properties of the copolymers were characterized by DMA, DSC, and TGA. Tensile properties were dominated by HBP <45% lignin content while lignin dominated >45% content. The copolymers glass transition temperature (T g ) increased with lignin content and lignin type did not play a significant role. Thermally stimulated dual shape memory effects (SME) of the copolymers were quantified by cyclic thermomechanical tests. All copolymers had shape fixity rate >95% and >90% shape recovery for all compositions. The copolymer shape memory transition temperature (T trans ) increased with lignin content and T trans was 20 C higher than T g . Lignin, a renewable resource, can be used as a netpoint segment in polymer systems with SME behavior.

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Section: Resultsmentioning

confidence: 99%

Lignin valorization by forming toughened thermally stimulated shape memory copolymeric elastomers: Evaluation of different fractionated industrial lignins

Sivasankarapillai

McDonald

2014

J of Applied Polymer Sci

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“…For the growing chain, this substituent is the SO 2 group placed between two aromatic rings. For the monomer, the opposite effect is used, as negative phenoxy group charge reduces electronegativity of the C–F end group by an electron delocalization effect, making it less reactive . A better electron‐withdrawing group than that of the growing chain was therefore needed.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Telechelic Poly(ether sulfone) Oligomers by Chain‐Growth Condensation Polymerization

Benhalima

Fürtös

Brisson

2013

Macro Chemistry & Physics

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The synthesis of telechelic poly(ether sulfone)s with methoxy end groups is reported. Molecular weights ranging from 1600 to 2800 g mol−1 and polydispersities of 1.1–1.2 are synthesized by chain‐growth condensation polymerization. The initiator is chosen by using semiempirical calculations and 19F NMR spectroscopy measurements. The polymers are characterized by NMR spectroscopy and matrix‐assisted laser desorption/ionization time of flight (MALDI‐TOF) mass spectrometry (MS), and are terminated by a methoxy group at one end and a fluorine at the other, and up to approximately 20% polymer of similar mass but slightly higher polydispersity, methoxy terminated at both ends, is present, along with less than 5% of polymer terminated at both ends by fluorine atoms. These do not need to be separated, and can be converted to methoxy‐ending telechelic blocks, yielding polyvalent, reactive rigid building blocks for copolymer synthesis.

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“…This interpretation is supported by the experimental results obtained from other a2 + b3 polycondensations published previously by Kricheldorf. [ 17,18 ] In summary, the results of this work clearly support an "egg-fi rst theory" of network formation at relatively low monomer concentrations, and any general theory of network formation has to consider that the initial monomer concentration plays a key role for the course of the polycondensation process.…”

Section: Resultsmentioning

confidence: 52%

Multicyclic Polyesters of Trimesic Acid and Alkanediols and the Theory of Network Formation

Kricheldorf

Weidner

Lahcini

2015

Macromol. Chem. Phys.

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Trimesoyl chloride is polycondensed with various α,ώ-alkanediols in dichloromethane at different concentrations using equifunctional feed ratios. As evidenced by MALDI-TOF (matrix assisted laser desorption/ionization-time of fl ight) mass spectrometry the soluble reaction products mainly consist of perfect multicyclic oligomers and polymers. The solphase extracted from the gels also consists of perfect multicycles. SEC (size exclusion chromatography) measurements show that both soluble reaction products and extracted solphases also contain a high molar mass fraction of perfect and nonperfect multicycles extending up to masses beyond 10 5 g mol −1 . When the polycondensation is stopped after a few minutes perfect multicycles are already detectable in the reaction mixture along with functional (multi)cyclic oligomers. These results prove that at initial monomer concentrations < 0.2 mol L −1 networks and large multicyclic polymers are synthesized from functional cyclic oligomers formed in early stages of the polycondensation and not from hyperbranched polymers. This interpretation is presented as "egg-fi rst theory" and compared with the "hen-fi rst theory" of Stockmayer and Flory.

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Polycondensation of ‘a − b_n’ or ‘a₂ + + b_n’ Monomers ‐ A Comparison

Cited by 37 publications

References 189 publications

Lignin valorization by forming toughened thermally stimulated shape memory copolymeric elastomers: Evaluation of different fractionated industrial lignins

Lignin valorization by forming toughened thermally stimulated shape memory copolymeric elastomers: Evaluation of different fractionated industrial lignins

Synthesis of Telechelic Poly(ether sulfone) Oligomers by Chain‐Growth Condensation Polymerization

Multicyclic Polyesters of Trimesic Acid and Alkanediols and the Theory of Network Formation

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