Silyl ether-coupled poly(ε-caprolactone)s with stepwise hydrolytic degradation profiles

Mu Wang, Q. Zhang, K. L. Wooley

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Silyl ether-coupled poly(ε-caprolactone)s (PCLs) with stepwise degradation profiles were synthesized via the cross-dehydrocoupling polymerizations between 1,4-bis(dimethylsilyl)benzene (BDSB) and telechelic, diol-terminated PCL macromonomers. With the presence of 10 wt % palladium on activated carbon as the catalyst, the condensations between BDSB and diol-terminated PCL macromonomers having molecular weights of 1200, 2010, and 5500 g/mol were performed in toluene at 100 °C under argon. Hydrogen was eliminated as the condensate upon the formation of silyl ether bonds linking the PCL blocks, yielding within 24 h, silyl ether-coupled PCLs of molecular mass 7590, 29900, and 29500 g/mol, respectively. The characterization of each polymer included 1H NMR, 13C NMR, and 29Si NMR spectroscopies, size exclusion chromatography (SEC), and differential scanning calorimetry. The hydrolytic degradation properties of the polymers in solution were studied, and the molecular weight reductions over time were monitored by SEC. The silyl ether linkages of the polymers underwent hydrolysis in the precense of mineral acids, whereas the PCL segments released from the cleavage of the labile silyl ether coupling unit did not undergo detectable molecular weight reduction over 15 days. In the presence of acetic acid, the silyl ether functionalities were cleaved with a half-life of 3 days; however, the PCL chain required reaction with trifluoroacetic acid to give a number-average molecular weight loss half-life of 4 days. The silyl ether-coupled PCLs underwent degradation in a gradient fashion, therefore, by a protocol that involved the addition of acetic acid for cleavage of the silyl ether functionalities, followed by further addition of trifluoroacetic acid to bring the hydrolysis of the silyl ether functionalities to completion and to trigger the degradation of PCL segments.

Original languageEnglish (US)
Pages (from-to)1206-1213
Number of pages8
JournalBiomacromolecules
Volume2
Issue number4
DOIs
StatePublished - 2001
Externally publishedYes

Fingerprint

Ether
Ethers
Degradation
Molecular Weight
Molecular weight
Trifluoroacetic acid
Weight Loss
Trifluoroacetic Acid
Polymers
Size exclusion chromatography
Benzene
Acetic acid
Acetic Acid
Gel Chromatography
Half-Life
Hydrolysis
Nuclear magnetic resonance
polycaprolactone
Argon
Differential Scanning Calorimetry

ASJC Scopus subject areas

  • Organic Chemistry
  • Biochemistry, Genetics and Molecular Biology(all)
  • Polymers and Plastics
  • Materials Chemistry

Cite this

Silyl ether-coupled poly(ε-caprolactone)s with stepwise hydrolytic degradation profiles. / Wang, Mu; Zhang, Q.; Wooley, K. L.

In: Biomacromolecules, Vol. 2, No. 4, 2001, p. 1206-1213.

Research output: Contribution to journalArticle

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abstract = "Silyl ether-coupled poly(ε-caprolactone)s (PCLs) with stepwise degradation profiles were synthesized via the cross-dehydrocoupling polymerizations between 1,4-bis(dimethylsilyl)benzene (BDSB) and telechelic, diol-terminated PCL macromonomers. With the presence of 10 wt {\%} palladium on activated carbon as the catalyst, the condensations between BDSB and diol-terminated PCL macromonomers having molecular weights of 1200, 2010, and 5500 g/mol were performed in toluene at 100 °C under argon. Hydrogen was eliminated as the condensate upon the formation of silyl ether bonds linking the PCL blocks, yielding within 24 h, silyl ether-coupled PCLs of molecular mass 7590, 29900, and 29500 g/mol, respectively. The characterization of each polymer included 1H NMR, 13C NMR, and 29Si NMR spectroscopies, size exclusion chromatography (SEC), and differential scanning calorimetry. The hydrolytic degradation properties of the polymers in solution were studied, and the molecular weight reductions over time were monitored by SEC. The silyl ether linkages of the polymers underwent hydrolysis in the precense of mineral acids, whereas the PCL segments released from the cleavage of the labile silyl ether coupling unit did not undergo detectable molecular weight reduction over 15 days. In the presence of acetic acid, the silyl ether functionalities were cleaved with a half-life of 3 days; however, the PCL chain required reaction with trifluoroacetic acid to give a number-average molecular weight loss half-life of 4 days. The silyl ether-coupled PCLs underwent degradation in a gradient fashion, therefore, by a protocol that involved the addition of acetic acid for cleavage of the silyl ether functionalities, followed by further addition of trifluoroacetic acid to bring the hydrolysis of the silyl ether functionalities to completion and to trigger the degradation of PCL segments.",
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