Broad‐line NMR and dynamic mechanical behavior of some aromatic polyesters

Frosini, Vittorio; Levita, G.; Landis, J. B.; Woodward, A. E.

doi:10.1002/pol.1977.180150204

Cited by 29 publications

(8 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Intercomparison of data in this way has invariably resulted in a deeper understanding of molecular processes in polymeric systems and works toward elucidation of the relationship between molecular motions and macroscopic properties. Similar, especially notable advantages have accrued from consideration of a range of materials in which the structure has been chemically modified in a systematic way (Slichter, 197 1;Woodward, Landis, and Frosini, 1972;Nogura and Wada, 1973;Frosini et al, 1977).…”

Section: A Unoriented Polymer Systemsmentioning

confidence: 97%

Recent advances in the NMR of solid polymers

McBrierty

Douglass²

1981

J. Polym. Sci. Macromol. Rev.

287

133

View full text Add to dashboard Cite

Section: A Unoriented Polymer Systemsmentioning

confidence: 97%

Recent advances in the NMR of solid polymers

McBrierty

Douglass²

1981

J. Polym. Sci. Macromol. Rev.

287

133

View full text Add to dashboard Cite

“…This LCP exhibits a Tg of 267uC, and a melting point of 610uC [28], which makes it rather intractable -the polymer in fact decomposes before it melts -and difficult to synthesize. In order to obtain a melt processable reactive oligomer, Mn has to drop to ,1000 g.mol 21 , which corresponds to n , 4.…”

Section: Reactive Oligomersmentioning

confidence: 99%

All‐aromatic liquid crystal thermosets: New high‐performance materials for structural applications

Dingemans

Knijnenberg

Iqbal

et al. 2006

Liquid Crystals Today

View full text Add to dashboard Cite

Over the past two decades, there has been an increasing interest in all-aromatic crosslinked liquid crystal (LC) systems for structural, electronics and coatings applications. In this paper we will give a brief overview of our work on oligomeric liquid crystals end-capped with phenylethynyl reactive end-groups. All reactive oligomers were synthesized using standard melt-condensation techniques and the final products form homogeneous nematic melts over a wide temperature range (220-400 uC). The reactive LC oligomers could be cured at elevated temperatures (310-400 uC) to form true rigid-rod nematic networks. As will be demonstrated, this oligomer approach allows us to design all-aromatic nematic networks with a variety of favorable physical, mechanical and processing characteristics. Depending on the backbone chemistry, and end-group concentration, we can access liquid crystal thermosets with Tg's between 110-280 uC and storage moduli (E') of 2-5 GPa. The oligomeric nature of our reactive LCs results in excellent melt processing characteristics (|g*| > 1 Pa.s at 100 rad.s 21 ) and allows for the processing of complex structures such as fiber-reinforced composites. Based on our current results we are convinced that reactive all-aromatic liquid crystals can be interesting alternatives over existing high-performance polymers such as polyarylether ketones (PEEK and PEKK) polyphenylenesulfide (PPS) and polyetherimides (PEIs).

show abstract

“…To further explore this concept, we selected a well‐known LCP concept based on readily available and cheap terephthalic acid (TA) and hydroquinone (HQ). Frosini et al13 showed that this polyester, that is, poly( p ‐phenylene terephthalate) (I) has a T m of ∼ 500 °C and a glass transition temperature ( T g ) of 267 °C. …”

Section: Introductionmentioning

confidence: 99%

All‐aromatic liquid crystalline thermosets with high glass transition temperatures

Iqbal

Norder

Mendes

et al. 2009

J. Polym. Sci. A Polym. Chem.

View full text Add to dashboard Cite

We have synthesized and characterized a new family of low melting allaromatic ester-based liquid crystal oligomers end-capped with reactive phenylethynyl end groups. In a consecutive, high-temperature step, the reactive end groups were thermally activated and polymerization was initiated. This reactive oligomer approach allows us to synthesize liquid crystal thermosets with outstanding mechanical and thermal properties, which are superior to well-known high-performance polymers such as PPS and PEEK. We have modified an intractable LC formulation based on hydroquinone and terephthalic acid, with M n ¼ 1000, 5000, and 9000 g mol À1 , and varied the backbone composition using isophthalic acid, resorcinol, 4hydroxy-benzoic acid, 6-hydroxy-2-naphthoic acid, and chlorohydroquinone. All fully cured polymers showed glass transition temperatures in the range of 164-275 C, and high storage moduli at room temperature ($ 5 GPa) and elevated temperature ($ 2 GPa at 200 C). All oligomers display nematic mesophases and in most cases, the nematic order is maintained after cure. Rheology experiments showed that the phenylethynyl end group undergoes predominantly chain extension below 340 C and crosslinking above this temperature. Highly aligned fibers could be spun from the nematic melt, and we found that the order parameter hP 2 i was not affected by the chain extension and crosslink chemistry.Scheme 2. Synthesis of the terephthalic acid (TA)-and hydroquinone (HQ)-based liquid crystalline oligomers with phenylethynyl end groups. The oligomers in series 1 are terminated with the more linear para-substituted reactive end groups, whereas the series 2 are end capped with the meta-substituted phenylethynyl functionalities. ALL-AROMATIC LIQUID CRYSTALLINE THERMOSETS

show abstract

Broad‐line NMR and dynamic mechanical behavior of some aromatic polyesters

Cited by 29 publications

References 6 publications

Recent advances in the NMR of solid polymers

Recent advances in the NMR of solid polymers

All‐aromatic liquid crystal thermosets: New high‐performance materials for structural applications

All‐aromatic liquid crystalline thermosets with high glass transition temperatures

Contact Info

Product

Resources

About