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Mechanism of Cryopolymerization: Diffusion-Controlled Polymerization in a Nonfrozen Microphase. An NMR Study

Kirsebom, Harald LU ; Rata, Gabriel LU ; Topgaard, Daniel LU ; Mattiasson, Bo LU and Galaev, Igor LU (2009) In Macromolecules 42(14). p.5208-5214
Abstract
Polymerization of dimethylacrylamide (DMAAm) cross-linked with PEG diacrylate was studied using H-1 NMR both in situ in a semi frozen system and in a supercooled aqueous system. The amount of nonfrozen microphase, in which polymerization proceeds, is defined by the concentration of the starting monomers and the freezing temperature, which depends on the depression in freezing temperature caused by dissolved osmolytes. However, despite there being identical initial concentrations in the nonfrozen microphase, at a chosen temperature of -10 degrees C the cryopolymerization proceeded at different rates depending on the size of the nonfrozen microphase. Further studies of the conditions in the nonfrozen microphase were performed by using pulsed... (More)
Polymerization of dimethylacrylamide (DMAAm) cross-linked with PEG diacrylate was studied using H-1 NMR both in situ in a semi frozen system and in a supercooled aqueous system. The amount of nonfrozen microphase, in which polymerization proceeds, is defined by the concentration of the starting monomers and the freezing temperature, which depends on the depression in freezing temperature caused by dissolved osmolytes. However, despite there being identical initial concentrations in the nonfrozen microphase, at a chosen temperature of -10 degrees C the cryopolymerization proceeded at different rates depending on the size of the nonfrozen microphase. Further studies of the conditions in the nonfrozen microphase were performed by using pulsed gradient spin echo (PGSE) to study the self-diffusion of solutes. Observations regarding the reaction rate were rationalized in terms of different degrees of long-range diffusion which was seen using PGSE. Cryopolymerization resulted in decreasing osmolyte concentration, and hence in gradual freezing of excess water as defined by the depression in freezing point caused by the remaining monomers. The NMR data provide a way of rationale predicting the effect of the monomer concentrations and freezing temperatures on the amount of nonfrozen microphase and its polymer concentration. These parameters define cryogel properties such as mechanical strength and porosity, which are evaluated using SEM and as flow resistance of cryogels. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Macromolecules
volume
42
issue
14
pages
5208 - 5214
publisher
The American Chemical Society
external identifiers
  • wos:000268175800040
  • scopus:67651089583
ISSN
0024-9297
DOI
10.1021/ma900566d
language
English
LU publication?
yes
id
ae1f0313-a969-4e21-9f64-12ed23568a3c (old id 1461459)
date added to LUP
2009-08-24 12:01:32
date last changed
2017-06-18 03:43:18
@article{ae1f0313-a969-4e21-9f64-12ed23568a3c,
  abstract     = {Polymerization of dimethylacrylamide (DMAAm) cross-linked with PEG diacrylate was studied using H-1 NMR both in situ in a semi frozen system and in a supercooled aqueous system. The amount of nonfrozen microphase, in which polymerization proceeds, is defined by the concentration of the starting monomers and the freezing temperature, which depends on the depression in freezing temperature caused by dissolved osmolytes. However, despite there being identical initial concentrations in the nonfrozen microphase, at a chosen temperature of -10 degrees C the cryopolymerization proceeded at different rates depending on the size of the nonfrozen microphase. Further studies of the conditions in the nonfrozen microphase were performed by using pulsed gradient spin echo (PGSE) to study the self-diffusion of solutes. Observations regarding the reaction rate were rationalized in terms of different degrees of long-range diffusion which was seen using PGSE. Cryopolymerization resulted in decreasing osmolyte concentration, and hence in gradual freezing of excess water as defined by the depression in freezing point caused by the remaining monomers. The NMR data provide a way of rationale predicting the effect of the monomer concentrations and freezing temperatures on the amount of nonfrozen microphase and its polymer concentration. These parameters define cryogel properties such as mechanical strength and porosity, which are evaluated using SEM and as flow resistance of cryogels.},
  author       = {Kirsebom, Harald and Rata, Gabriel and Topgaard, Daniel and Mattiasson, Bo and Galaev, Igor},
  issn         = {0024-9297},
  language     = {eng},
  number       = {14},
  pages        = {5208--5214},
  publisher    = {The American Chemical Society},
  series       = {Macromolecules},
  title        = {Mechanism of Cryopolymerization: Diffusion-Controlled Polymerization in a Nonfrozen Microphase. An NMR Study},
  url          = {http://dx.doi.org/10.1021/ma900566d},
  volume       = {42},
  year         = {2009},
}