Macrocycles 25. Cyclic poly(ether sulfone)s derived from 4-tert-butylcatechol

Kricheldorf, Hans R.; Vakhtangishvili, Lali; Schwarz, Gert; Schulz, Günter; Krüger, Ralf-Peter

doi:10.1016/s0032-3861(03)00410-5

Cited by 40 publications

(44 citation statements)

References 13 publications

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“…No linear chains were observed in this mass range. 20 Polycondensations of free or silylated bisphenol-A with 4,4 0 -difluorodiphenyl sulfone gave similar results, 39 but the mass range of the MT mass spectra was limited to 13 kDa. With less reactive 4,4 0 -dichlorodiphenyl sulfone, conversions above 99.9% are difficult to achieve with the consequence that the extent of cyclization is lower.…”

Section: Figure 1 Number Fraction Of Rings (N R ) Versus Conversion (P)mentioning

confidence: 88%

“…Unfavorable cases MT mass spectra of virgin reaction products may cover the mass range up to 20 kDa. [20][21][22] However, a polycondensate with a M n of 10-25 kDa, as it is typical for several technical products, contains a small fraction of chains having masses above 50 kDa, which escape from any mass-spectroscopy identification at this time.…”

Section: Figure 1 Number Fraction Of Rings (N R ) Versus Conversion (P)mentioning

confidence: 99%

“…20,[39][40][41][42] Silylation of the diphenols reduces the risk of oxidation and allows for polycondensations in bulk or in concentrated solutions. Particular informative were polycondensations of silylated 4-tertbutylcatechol with 4,4 0 -difluorodiphenyl sulfone (Scheme 6), because the resulting poly(ether sulfone)s gave extraordinarily good MT mass spectra.…”

Section: Figure 1 Number Fraction Of Rings (N R ) Versus Conversion (P)mentioning

confidence: 99%

“…An initiation and ring-opening polymerization process analogous to that for primary amines yields peptide chains with two reactive endgroups (Scheme 28). It is known for many decades 109 that imidazolides of carboxylic acids are several orders of magnitude more electrophilic than normal amide groups and react easily with amines at [20][21][22] C, and with alcohol or water at higher temperatures. Therefore, the imidazole-initiated peptide chains can react with each other producing chain extension by condensation steps or they can cyclize (Scheme 28).…”

Section: Highlightmentioning

confidence: 99%

“…Quite recently, a ROP of D,L-lactide catalyzed by a nucleophilic carbene at [20][21][22][23][24][25] C in solution was reported. 188 Up to 15 kDa, the MT mass spectra exclusively displayed peaks of cycles and proved total equilibration.…”

Section: Ring-ring Equilibrationmentioning

confidence: 99%

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Cyclic polymers: Synthetic strategies and physical properties

Kricheldorf

2009

J. Polym. Sci. A Polym. Chem.

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400

442

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Syntheses of cyclic polymers including cyclic homopolymers, cyclic block copolymers, sun-shaped polymers, and tadpole polymers are discussed on the basis of a differentiation between synthetic methods and synthetic strategies (e.g., polycondensation, ring-ring equilibration, or ring-expansion polymerization). Furthermore, all synthetic methods are classified as kinetically or thermodynamically controlled reactions. Characteristic properties of cyclic polymers such as smaller hydrodynamic volume, lower melt viscosities, and higher thermostabilities are compared to the properties of their linear counterparts. Furthermore, the nanophase separation of cyclic diblock copolymers is discussed.

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Section: Figure 1 Number Fraction Of Rings (N R ) Versus Conversion (P)mentioning

confidence: 88%

Section: Figure 1 Number Fraction Of Rings (N R ) Versus Conversion (P)mentioning

confidence: 99%

Section: Figure 1 Number Fraction Of Rings (N R ) Versus Conversion (P)mentioning

confidence: 99%

Section: Highlightmentioning

confidence: 99%

Section: Ring-ring Equilibrationmentioning

confidence: 99%

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Cyclic polymers: Synthetic strategies and physical properties

Kricheldorf

2009

J. Polym. Sci. A Polym. Chem.

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400

442

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Polymers of Carbonic Acid, 31. Cyclic Polycarbonates by Hydrolytic Polycondensation of Bisphenol-A Bischloroformate

Kricheldorf¹,

Böhme

Schwarz

et al. 2002

Macromol. Rapid Commun.

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The hydrolytic polycondensation of bisphenol‐A bischloroformate in NaOH/CH2Cl2 was studied using triethylamine as the catalyst. Reaction conditions were optimized towards high molar masses. The isolated polycarbonates were characterized by means of SEC and MALDI‐TOF mass spectrometry. The fraction of cyclic polycarbonates strongly increased with higher molecular weights and in the best sample only cycles were detectable (up to 50 000 Da). The largest cycles can compete with cyclic DNS of microorganisms.

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Distinct topography of erosion and new bone formation in achilles tendon enthesitis: Implications for understanding the link between inflammation and bone formation in spondylarthritis

McGonagle¹,

Wakefield²,

Tan³

et al. 2008

Arthritis & Rheumatism

115

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Objective. This study combined ultrasonography of the Achilles tendon enthesis at different stages of spondylarthritis (SpA) with microanatomic studies of normal cadaveric entheses, with the aim of exploring the relationship between bone erosion and new bone formation in enthesitis.Methods. Thirty-seven patients with SpA and Achilles tendon enthesitis (20 with early SpA and 17 with chronic SpA) and 10 normal control subjects underwent ultrasound scanning. The presence of bone erosion and spur formation was recorded at 3 sites: the proximal and distal halves of the enthesis and the adjacent calcaneal superior tuberosity. Parallel histologic analysis was performed on cadaveric Achilles tendon entheses to determine whether regional variations in bone density and trabecular architecture in relation to fibrocartilage distribution are related to disease patterns.Results. Bone erosion in patients with early SpA occurred at either the proximal insertion or the superior tuberosity (11 of 20 patients; P < 0.001 versus distal enthesis). Very small spurs, which were present almost exclusively at the distal enthesis, were evident in patients with early SpA and in normal control subjects. However, large spurs were evident distally only in patients with chronic SpA (9 of 17 patients, compared with none of 20 patients with early SpA; P < 0.0001). Histologic studies showed that aged normal individuals had small spurs at the corresponding location. The bone-to-marrow ratio was also significantly lower in the regions prone to erosions (P < 0.05).Conclusion. Bone erosion in association with Achilles tendon enthesitis in SpA is anatomically uncoupled from bone formation-the 2 processes are topographically and temporally distinct. We thus conclude that disease patterns in SpA are related to normal enthesis structure and biomechanics.

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Macrocycles 25. Cyclic poly(ether sulfone)s derived from 4-tert-butylcatechol

Cited by 40 publications

References 13 publications

Cyclic polymers: Synthetic strategies and physical properties

Cyclic polymers: Synthetic strategies and physical properties

Polymers of Carbonic Acid, 31. Cyclic Polycarbonates by Hydrolytic Polycondensation of Bisphenol-A Bischloroformate

Distinct topography of erosion and new bone formation in achilles tendon enthesitis: Implications for understanding the link between inflammation and bone formation in spondylarthritis

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