Rapid and quantitative de- tert-butylation for poly(acrylic acid) block copolymers and influence on relaxation of thermoassociated transient networks

Alexei D. Filippov, Ilse A. van Hees, Remco Fokkink, Ilja K. Voets, Marleen Kamperman

Onderzoeksoutput: Bijdrage aan tijdschriftTijdschriftartikelAcademicpeer review

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Uittreksel

The synthesis of charged polymers often requires the polymerization of protected monomers, followed by a polymer-analogous reaction to the polyelectrolyte product. We present a mild, facile method to cleave tert-butyl groups from poly(tert-butyl acrylate) blocks that yields poly(acrylic acid) (pAA) blocks free of traces of the ester. The reaction utilizes a slight excess of HCl in hexafluoroisopropanol (HFIP) at room temperature and runs to completion within 4 h. We compare deprotection in HFIP with the common TFA/DCM method and show that the latter does not yield clean pAA. We show the effect of complete tert-butyl cleavage on a ABA triblock copolymer, where poly(N-isopropylacrylamide) (pNIPAM) is A and pAA is B, by means of viscosimetry, DLS, and SAXS on solutions above overlap. The pNIPAM blocks dehydrate, and their increased self-affinity above the lower critical solution temperature (LCST) results in network formation by the triblocks. This manifests itself as an increase in viscosity and a slowing down of the first-order correlation function in light scattering. However, this stickering effect manifests itself exclusively when the pAA block is tert-butyl-free. Additionally, SAXS shows that the conformational properties of tert-butyl-free pAA copolymers are markedly different from those with residual esters. Thus, we illustrate a surprising effect of hydrophobic impurities that act across blocks and assert the usefulness of HCl/HFIP in pAA synthesis.

Originele taal-2Engels
Pagina's (van-tot)8316-8323
Aantal pagina's8
TijdschriftMacromolecules
Volume51
Nummer van het tijdschrift20
DOI's
StatusGepubliceerd - 23 okt 2018

Vingerafdruk

carbopol 940
Block copolymers
Acrylics
Esters
Acids
Polymers
Polyelectrolytes
Light scattering
Copolymers
Monomers
Polymerization
Viscosity
Impurities
Temperature
hexafluoroisopropanol

Citeer dit

Filippov, Alexei D. ; van Hees, Ilse A. ; Fokkink, Remco ; Voets, Ilja K. ; Kamperman, Marleen. / Rapid and quantitative de- tert-butylation for poly(acrylic acid) block copolymers and influence on relaxation of thermoassociated transient networks. In: Macromolecules. 2018 ; Vol. 51, Nr. 20. blz. 8316-8323.
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Rapid and quantitative de- tert-butylation for poly(acrylic acid) block copolymers and influence on relaxation of thermoassociated transient networks. / Filippov, Alexei D.; van Hees, Ilse A.; Fokkink, Remco; Voets, Ilja K.; Kamperman, Marleen.

In: Macromolecules, Vol. 51, Nr. 20, 23.10.2018, blz. 8316-8323.

Onderzoeksoutput: Bijdrage aan tijdschriftTijdschriftartikelAcademicpeer review

TY - JOUR

T1 - Rapid and quantitative de- tert-butylation for poly(acrylic acid) block copolymers and influence on relaxation of thermoassociated transient networks

AU - Filippov, Alexei D.

AU - van Hees, Ilse A.

AU - Fokkink, Remco

AU - Voets, Ilja K.

AU - Kamperman, Marleen

PY - 2018/10/23

Y1 - 2018/10/23

N2 - The synthesis of charged polymers often requires the polymerization of protected monomers, followed by a polymer-analogous reaction to the polyelectrolyte product. We present a mild, facile method to cleave tert-butyl groups from poly(tert-butyl acrylate) blocks that yields poly(acrylic acid) (pAA) blocks free of traces of the ester. The reaction utilizes a slight excess of HCl in hexafluoroisopropanol (HFIP) at room temperature and runs to completion within 4 h. We compare deprotection in HFIP with the common TFA/DCM method and show that the latter does not yield clean pAA. We show the effect of complete tert-butyl cleavage on a ABA triblock copolymer, where poly(N-isopropylacrylamide) (pNIPAM) is A and pAA is B, by means of viscosimetry, DLS, and SAXS on solutions above overlap. The pNIPAM blocks dehydrate, and their increased self-affinity above the lower critical solution temperature (LCST) results in network formation by the triblocks. This manifests itself as an increase in viscosity and a slowing down of the first-order correlation function in light scattering. However, this stickering effect manifests itself exclusively when the pAA block is tert-butyl-free. Additionally, SAXS shows that the conformational properties of tert-butyl-free pAA copolymers are markedly different from those with residual esters. Thus, we illustrate a surprising effect of hydrophobic impurities that act across blocks and assert the usefulness of HCl/HFIP in pAA synthesis.

AB - The synthesis of charged polymers often requires the polymerization of protected monomers, followed by a polymer-analogous reaction to the polyelectrolyte product. We present a mild, facile method to cleave tert-butyl groups from poly(tert-butyl acrylate) blocks that yields poly(acrylic acid) (pAA) blocks free of traces of the ester. The reaction utilizes a slight excess of HCl in hexafluoroisopropanol (HFIP) at room temperature and runs to completion within 4 h. We compare deprotection in HFIP with the common TFA/DCM method and show that the latter does not yield clean pAA. We show the effect of complete tert-butyl cleavage on a ABA triblock copolymer, where poly(N-isopropylacrylamide) (pNIPAM) is A and pAA is B, by means of viscosimetry, DLS, and SAXS on solutions above overlap. The pNIPAM blocks dehydrate, and their increased self-affinity above the lower critical solution temperature (LCST) results in network formation by the triblocks. This manifests itself as an increase in viscosity and a slowing down of the first-order correlation function in light scattering. However, this stickering effect manifests itself exclusively when the pAA block is tert-butyl-free. Additionally, SAXS shows that the conformational properties of tert-butyl-free pAA copolymers are markedly different from those with residual esters. Thus, we illustrate a surprising effect of hydrophobic impurities that act across blocks and assert the usefulness of HCl/HFIP in pAA synthesis.

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U2 - 10.1021/acs.macromol.8b01440

DO - 10.1021/acs.macromol.8b01440

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JO - Macromolecules

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IS - 20

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