PH-induced phase transition control of thermoresponsive nano-micelles possessing outermost surface sulfonamide moieties

Masamichi Nakayama, Yayoi Kawahara, Jun Akimoto, Hideko Kanazawa, Teruo Okano

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

Diblock copolymer comprising thermoresponsive poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) (PIPAAm-co-DMAAm) and hydrophobic poly(benzyl methacrylate) blocks was prepared by reversible addition-fragmentation chain transfer radical polymerization. Terminal functionalization of thermoresponsive blocks with either pH-responsive sulfadimethoxine (SD) or hydroxyl groups was performed through coupling reactions with thiol groups exposed by the aminolysis of dithiobenzoate groups located at P(IPAAm-co-DMAAm) termini. Outermost surface functionalized polymeric micelles were formed through the multi-assemblies of end-functional diblock copolymers with low critical micelle concentration (3.1-3.3mg/L) regardless of their terminal groups. Variety of outermost surface functional groups had little influence on nano-scale diameters of approximately 19nm at various pH values. Although the zeta-potentials of nonionic (phenyl and hydroxyl) surface micelles were independent of pH values ranged 8.1-5.4, those of SD-surface polymeric micelles changed from -12 to -4mV with reducing pH value, which caused by the protonation of surface SD units (pK a=6.2). In addition, lower critical solution temperature (LCST) of SD-surface micelles significantly shifted from 38.6 to 22.6°C with lowering pH from 5.4 to 8.1. These pH-induced lower LCST shifts were caused by extremely increasing surface hydrophobicity through the charge neutralization of SD moieties and the subsequent promoted dehydration of corona-forming polymer chains. These results indicated that the phase transition behavior of thermoresponsive nano-micelles was particularly controlled by modulating the properties of outermost surface chemistry via specific signals (e.g., pH, light, and biomolecular interaction).

Original languageEnglish
Pages (from-to)12-19
Number of pages8
JournalColloids and Surfaces B: Biointerfaces
Volume99
DOIs
Publication statusPublished - 2012 Nov 1

Fingerprint

Phase Transition
Sulfonamides
Sulfadimethoxine
Micelles
micelles
Phase transitions
Hydroxyl Radical
Block copolymers
copolymers
Temperature
Surface Properties
Critical micelle concentration
Protonation
Zeta potential
Hydrophobicity
Free radical polymerization
Surface chemistry
Dehydration
Hydrophobic and Hydrophilic Interactions
Sulfhydryl Compounds

Keywords

  • Block copolymer
  • PH-response
  • Poly(N-isopropylacrylamide)
  • Sulfadimethoxine
  • Thermoresponsive polymeric micelle

ASJC Scopus subject areas

  • Biotechnology
  • Colloid and Surface Chemistry
  • Physical and Theoretical Chemistry
  • Surfaces and Interfaces

Cite this

PH-induced phase transition control of thermoresponsive nano-micelles possessing outermost surface sulfonamide moieties. / Nakayama, Masamichi; Kawahara, Yayoi; Akimoto, Jun; Kanazawa, Hideko; Okano, Teruo.

In: Colloids and Surfaces B: Biointerfaces, Vol. 99, 01.11.2012, p. 12-19.

Research output: Contribution to journalArticle

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abstract = "Diblock copolymer comprising thermoresponsive poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) (PIPAAm-co-DMAAm) and hydrophobic poly(benzyl methacrylate) blocks was prepared by reversible addition-fragmentation chain transfer radical polymerization. Terminal functionalization of thermoresponsive blocks with either pH-responsive sulfadimethoxine (SD) or hydroxyl groups was performed through coupling reactions with thiol groups exposed by the aminolysis of dithiobenzoate groups located at P(IPAAm-co-DMAAm) termini. Outermost surface functionalized polymeric micelles were formed through the multi-assemblies of end-functional diblock copolymers with low critical micelle concentration (3.1-3.3mg/L) regardless of their terminal groups. Variety of outermost surface functional groups had little influence on nano-scale diameters of approximately 19nm at various pH values. Although the zeta-potentials of nonionic (phenyl and hydroxyl) surface micelles were independent of pH values ranged 8.1-5.4, those of SD-surface polymeric micelles changed from -12 to -4mV with reducing pH value, which caused by the protonation of surface SD units (pK a=6.2). In addition, lower critical solution temperature (LCST) of SD-surface micelles significantly shifted from 38.6 to 22.6°C with lowering pH from 5.4 to 8.1. These pH-induced lower LCST shifts were caused by extremely increasing surface hydrophobicity through the charge neutralization of SD moieties and the subsequent promoted dehydration of corona-forming polymer chains. These results indicated that the phase transition behavior of thermoresponsive nano-micelles was particularly controlled by modulating the properties of outermost surface chemistry via specific signals (e.g., pH, light, and biomolecular interaction).",
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AU - Nakayama, Masamichi

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AU - Akimoto, Jun

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AU - Okano, Teruo

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AB - Diblock copolymer comprising thermoresponsive poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) (PIPAAm-co-DMAAm) and hydrophobic poly(benzyl methacrylate) blocks was prepared by reversible addition-fragmentation chain transfer radical polymerization. Terminal functionalization of thermoresponsive blocks with either pH-responsive sulfadimethoxine (SD) or hydroxyl groups was performed through coupling reactions with thiol groups exposed by the aminolysis of dithiobenzoate groups located at P(IPAAm-co-DMAAm) termini. Outermost surface functionalized polymeric micelles were formed through the multi-assemblies of end-functional diblock copolymers with low critical micelle concentration (3.1-3.3mg/L) regardless of their terminal groups. Variety of outermost surface functional groups had little influence on nano-scale diameters of approximately 19nm at various pH values. Although the zeta-potentials of nonionic (phenyl and hydroxyl) surface micelles were independent of pH values ranged 8.1-5.4, those of SD-surface polymeric micelles changed from -12 to -4mV with reducing pH value, which caused by the protonation of surface SD units (pK a=6.2). In addition, lower critical solution temperature (LCST) of SD-surface micelles significantly shifted from 38.6 to 22.6°C with lowering pH from 5.4 to 8.1. These pH-induced lower LCST shifts were caused by extremely increasing surface hydrophobicity through the charge neutralization of SD moieties and the subsequent promoted dehydration of corona-forming polymer chains. These results indicated that the phase transition behavior of thermoresponsive nano-micelles was particularly controlled by modulating the properties of outermost surface chemistry via specific signals (e.g., pH, light, and biomolecular interaction).

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