Unexpected Large Depression of VPTT of a PNIPAM Microgel by Low Concentration of PVA

Tang, Zhuo; Weng, Junying; Guan, Ying; Zhang, Yongjun

doi:10.1002/macp.201700364

Cited by 12 publications

(20 citation statements)

References 54 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, the VPTT of (PNIPAM core-P(NIPAM-co-2-acrylamido-phenylboronic acid (AAPBA))-shell) microgel, which was obtained by modifying a P(NIPAM-acrylic acid (AAc)) shell with 3-aminophenylboronic acid (APBA), was drastically reduced by the addition of a low concentration of PVA. It was proposed that the chemical adsorption of PVA chains onto the P(NIPAM-2-AAPBA) microgel shortened the distance between the PVA and PNIPAM chains and it enhanced the interaction between P(NIPAM-2-AAPBA) and PVA [46].…”

Section: Vptt and Its Sharpness Of Microgelsmentioning

confidence: 99%

On Going to a New Era of Microgel Exhibiting Volume Phase Transition

Kawaguchi

2020

Gels

View full text Add to dashboard Cite

The discovery of phenomena of volume phase transition has had a great impact not only on bulk gels but also on the world of microgels. In particular, research on poly(N-isopropylacrylamide) (PNIPAM) microgels, whose transition temperature is close to body temperature, has made remarkable progress in almost 35 years. This review presents some breakthrough findings in microgels that exhibit volume phase transitions and outlines recent works on the synthesis, structural analysis, and research direction of microgels.

show abstract

Section: Vptt and Its Sharpness Of Microgelsmentioning

confidence: 99%

On Going to a New Era of Microgel Exhibiting Volume Phase Transition

Kawaguchi

2020

Gels

View full text Add to dashboard Cite

show abstract

“…We then coupled the carboxylic acid groups in the microgels with 11-azido-3,6,9-trioxaundecan-1-amine or propargylamine under N -(3-dimethylaminopropyl)- N ′-ethylcarbodiimide hydrochloride (EDC) catalysis to introduce azide or alkyne groups (Scheme A). A similar procedure was previously used to introduce other functional groups, e.g., phenylboronic acids, into the PNIPAM microgels. − The successful modification of microgels was confirmed by the appearance of new peaks at 3.77 and 3.56 ppm (−N–CH 2 –C H 2 –O–C H 2 –C H 2 –O–C H 2 –C H 2 –O–CH 2 –CH 2 –N 3 ) or 2.73 ppm (−N–CH 2 –CC– H ) in the 1 H NMR spectra of the corresponding microgels (Figure S2). Considering the remaining amounts of AAc in the microgels, as determined again by pH titration, ∼47.0 or ∼37.3% of the AAc groups were coupled with azide or alkyne groups, respectively (Figures S3 and S4).…”

Section: Resultsmentioning

confidence: 78%

Layer-by-Layer Assembly of Microgel Colloidal Crystals via Photoinitiated Alkyne–Azide Click Reaction

2019

Self Cite

View full text Add to dashboard Cite

Layer-by-layer (LBL) assembly of colloidal crystals (CCs) allows for the fine control of the thickness and architecture of the resulting crystals. Various methods have been developed for the LBL assembly of CCs of hard spheres. However, these methods are inapplicable for microgel CCs owing to the softness and deformability of microgel spheres. In this study, a method was proposed for the LBL assembly of microgel CCs. To build the first monolayer, azide-modified microgel spheres were assembled into a three-dimensional (3D) CC. The first 111 plane of the 3D CC close to the substrate was then fixed in situ onto the substrate via photoinitiated alkyne–azide click reaction between the azide groups on the microgels and the alkyne groups on the substrate surface. The removal of unbonded particles resulted in a microgel monolayer with a high degree of order. The second monolayer was assembled in a similar manner, i.e., a 3D microgel CC was initially assembled followed by in situ fixation of the first 111 plane of the 3D crystal with the underlying microgel monolayer by photoinitiated alkyne–azide click reaction. For this purpose, instead of azide-modified microgel spheres, alkyne-modified microgel spheres were used for the assembly of the second layer. Confocal studies confirmed that the second monolayer was located on top of the first layer. When the lattice constant of the 3D CC approximated that of the underlying microgel monolayer, the second monolayer exhibited a high degree of order. Repeating this process led to alternating deposition of highly ordered monolayers of azide-modified and alkyne-modified microgels onto the substrate. Similar to the microgel CCs obtained by the self-assembly of microgel spheres in bulky dispersions, face-centered cubic and hexagonal-close-packed structures also coexisted in the LBL-assembled microgel CCs.

show abstract

“…Copolymer Synthesis and Characterization. We recently found that the VPTT of P(NIPAM-2-AAPBA) microgel can be significantly decreased by PVA 28 and glucose 29 because the additive molecules can be drawn close to the PNIPAM chains in the microgel via the formation of phenylboronate ester bonds. Here we studied whether PVA can influence the thermal behaviors of linear polymers.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…8 We recently found that the capability of an additive to shift phase transition temperature could be remarkably magnified by shortening the distance between the additive molecules and the thermosensitive polymer chains. 28,29 As a polymeric additive, poly(vinyl alcohol) (PVA) can change the LCST/ VPTT to a very small degree. 30−33 It was reported that 5 wt % PVA can only decrease the VPTT of PNIPAM hydrogel by ∼4 °C.…”

Section: ■ Introductionmentioning

confidence: 99%

“…31 Very differently, the VPTT of the surface layer of poly(N-isopropylacrylamide-co-2-acrylamidophenylboronic acid) (P(NIPAM-2-AAPBA)) microgel can be decreased by 8.4 °C in the presence of a very low concentration of PVA (only 0.004 wt %) because PVA can bind with PBA groups on the microgel surface and become close to PNIPAM chains. 28 Similarly, because glucose can bind with PBA groups in the P(NIPAM-2-AAPBA) microgel and become close to PNIPAM chains, it depresses the VPTT of P(NIPAM-2-AAPBA) microgel much more efficiently than the PNIPAM microgel. 29 In this work we systematically investigated the effect of PVA on the thermosensitive behaviors of a series of copolymers of acrylamide (AAm), N,N-dimethylacrylamide (DMAA), and 3-(acrylamido)phenylboronic acid (3-AAPBA), P(AAm-DMAA-3-AAPBA), in layer-by-layer (LBL) assembled films.…”

Section: ■ Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Extraordinarily Large LCST Depression Converts Nonthermosensitive Polymer to Thermosensitive

Tian

Guan

et al. 2018

Macromolecules

Self Cite

View full text Add to dashboard Cite

A facile method to tune the phase transition temperature of thermosensitive polymers is to introduce an additive; however, the influence of additives is usually limited. Here the influence of poly(vinyl alcohol) (PVA), a polymeric additive, on thermal behavior of copolymers of acrylamide (AAm), N,N-dimethylacrylamide (DMAA), and 3-(acrylamido)phenylboronic acid (3-AAPBA), P(AAm-DMAA-3-AAPBA), was studied. With increasing AAm content, the phase transition temperature of the copolymers increases gradually. They finally become nonthermosensitive when AAm content exceeds 20 mol %. To study the influence of PVA on the copolymers, they were incorporated into thin films via layer-by-layer (LBL) assembly, using phenylboronate ester bonds between them as a driving force. Because the two polymers in the films were drawn very close to each other, the ability of PVA to depress phase transition temperature of copolymer is significantly amplified. As a result, an unprecedented large depression on phase transition temperature was observed. As an example, the phase transition temperature of P(AAm-DMAA-3-AAPBA)15 is significantly decreased from 86 °C in solution to 14 °C in the LBL film, corresponding to a 72 °C decrease. More importantly, some copolymers that do not exhibit thermosensitive behaviors in solution can be turned to be thermosensitive, as their phase transition temperature can be decreased from ≥100 to <100 °C due to the extraordinarily large ability of PVA to depress the phase transition temperature. Consequently, films from these nonthermosensitive copolymers also present a heat-induced phase transition.

show abstract

Unexpected Large Depression of VPTT of a PNIPAM Microgel by Low Concentration of PVA

Cited by 12 publications

References 54 publications

On Going to a New Era of Microgel Exhibiting Volume Phase Transition

On Going to a New Era of Microgel Exhibiting Volume Phase Transition

Layer-by-Layer Assembly of Microgel Colloidal Crystals via Photoinitiated Alkyne–Azide Click Reaction

Extraordinarily Large LCST Depression Converts Nonthermosensitive Polymer to Thermosensitive

Contact Info

Product

Resources

About