Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Single crystal morphology of star polyesters with crystallisable poly(ε–caprolactone) arms
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2005 (English)In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 46, no 16, 5992-6000 p.Article in journal (Refereed) Published
Abstract [en]

Star-branched polymers consisting of poly(epsilon-caprolactone) (PCL) attached to third generation dendrimer, hyperbranched and dendron cores have been studied together with linear PCL analogues. The degree of polymerisation of the PCL arms of the star-branched polymers ranged from 14 to 81. Single crystals were grown from dilute solution and studied by transmission electron microscopy. Single crystals of linear PCL were multilayer hexagons with flat or slightly curved {110} and {100} faces. These single crystals were larger along [010] than along [100]. Single crystals of star-branched PCL showed the same basic shape, but with many crystallographic and irregular steps on the lateral crystal faces. The width of the micro-faces was typically 100-300 nm. These single crystals were more extended along [100] than along [010]. It is proposed that the high fold surface free energy and the constrained character of the star-branched polymers favour the formation of steps on the growth faces. Globular polycrystalline aggregates were also observed. They originated from a more concentrated polymer phase following phase separation of the solution. In the case of the star-branched polymers, lamellar branching was observed with a 30 angle between the crystals arms.

Place, publisher, year, edition, pages
2005. Vol. 46, no 16, 5992-6000 p.
Keyword [en]
star-branched poly(epsilon-caprolactone), single crystal, transmission electron microscopy
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-5972DOI: 10.1016/j.polymer.2005.05.083ISI: 000230714200019Scopus ID: 2-s2.0-21744456720OAI: oai:DiVA.org:kth-5972DiVA: diva2:10524
Note
QC 20100914Available from: 2006-06-07 Created: 2006-06-07 Last updated: 2010-09-14Bibliographically approved
In thesis
1. Crystallization in Constrained Polymer Structures: Approaching the Unsolved Problems in Polymer Crystallization
Open this publication in new window or tab >>Crystallization in Constrained Polymer Structures: Approaching the Unsolved Problems in Polymer Crystallization
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The knowledge regarding certain issues in polymer crystallization e.g. the possible existence of short–lived mesophases remains inconclusive due to experimental limitations. Polymers undergo chain folding upon crystallization, which introduces some complications that are not found in crystallization of low molar mass materials. Chain–folded crystals are far from their equilibrium shape and they rearrange rapidly at the crystallization temperature. This, together with the slow experimental techniques traditionally used, impedes the observation of the originally formed structures. To approach this problem, molecularly constrained polymer structures (in which the crystallizing chains are fixed at one end whereas the other end is free to move) have been studied by X–ray diffraction, differential scanning calorimetry, polarized optical microscopy, transmission electron microscopy and atomic force microscopy.

The crystallization studies performed in star–branched polyesters showed that the dendritic cores have a pronounced effect on the crystallization of the linear poly(ε–caprolactone) (PCL) arms attached to them. The star–branched polymers showed slower crystal rearrangement, higher equilibrium melting point, higher fold surface free energy, moderately lower crystallinity, and a greater tendency to form spherulites in comparison with linear PCL. The crystal unit cell was the same in both linear and star–branched PCL. Single crystals of the star–branched polymers were more irregular and showed smoother fold surfaces than linear PCL crystals. No sectorial preference was observed in the crystals of the star–branched polymers upon melting while the single crystals of linear PCL showed earlier melting in the {100} sectors than in the {110} sectors. Some of the differences observed can be attributed to the dendritic cores, which must be placed in the vicinity of the fold surface and thus influence the fold surface structure, the possibility of major crystal rearrangement and the presence of a significant cilia phase during crystal growth causing diverging crystal lamellae and consequent spherulite formation. The attachment of the many crystallizable chains to a single core reduces the melt entropy, which explains the higher equilibrium melting point of star–branched PCL.

The crystallization behavior of a series of poly(ethylene oxybenzoate)s was also studied. The polymers showed a profound tendency for crystal rearrangement during melting even at high heating rates. The Hoffman–Weeks extrapolation method was found to be unsuitable to calculate the equilibrium melting point of the samples studied because the melting point vs. crystallization temperature data were sensitive to the variations in crystallisation time, which led to significant variations in the equilibrium melting points obtained.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. 72 p.
Series
Trita-FPT-Report, ISSN 1652-2443 ; 2006:17
Keyword
Crystallization, Constrained structures, poly(ε–caprolactone), poly(ethylene oxybenzoate).
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-4041 (URN)91-7178-375-X (ISBN)
Public defence
2006-06-16, Sal K2, Teknikringen 28, Stockholm, 14:00
Opponent
Supervisors
Note
QC 20100914Available from: 2006-06-07 Created: 2006-06-07 Last updated: 2010-09-14Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textScopushttp://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TXW-4GD4SMG-P&_user=4478132&_handle=V-WA-A-W-CB-MsSAYWA-UUA-U-AACWWUBDWC-AAVEDYVCWC-EADYUUWDV-CB-U&_fmt=summary&_coverDate=07%2F25%2F2005&_rdoc=20&_orig=browse&_srch=%23toc%235601%232005%23999539983%23601146!&_cdi=5601&view=c&_acct=C000034958&_version=1&_urlVersion=0&_userid=4478132&md5=ce39c8a2ed6038f8fccf8c72bff35c23

Search in DiVA

By author/editor
Núñez, EugeniaGedde, Ulf W.
By organisation
Fibre and Polymer Technology
In the same journal
Polymer
Polymer Chemistry

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 62 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf