Effect of tacticity and molecular weight on the rheological properties of poly(<i>N</i>-isopropylacrylamide) gels in benzyl alcohol

Biswas, Chandra Sekhar; Wu, Yuhang; Wang, Qiao; Du, Lei; Mitra, Kheyanath; Ray, Biswajit; Yan, Zhi-Chao; Du, Bing; Stadler, Florian J.

doi:10.1122/1.5006807

Cited by 11 publications

(13 citation statements)

References 56 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For both m and Hm series, G ’ slightly decreases with isotacticity, showing a scaling power law slope −2.2 and −1.2, respectively. This dependence is opposite to the case of PNIPAMs in benzyl alcohol [34], where the plateau G ’ increases with isotacticity. However, we note that PNIPAM/benzyl alcohol gel is transparent, while the PNIPAM/IL gel is opaque.…”

Section: Resultscontrasting

confidence: 62%

“…Upon further heating, other segments are also dehydrated, so that the whole chain transfers to globules and the system becomes turbid. Such partial phase separation was also reported in isotactic-rich PNIPAM/benzyl alcohol blends [34], where a transparent gel was formed below the UCST-type transition temperatures, and the transition temperature increases with the meso-diad content. As molten salts, ILs have different interactions with PNIPAM in comparison to water and organic solvents.…”

Section: Introductionsupporting

confidence: 72%

“…This situation is intensified with increasing isotacticity, reducing the number of connections among globules, and thus thinning out the network. The storage moduli of Hm are higher than m series, reflecting a better-connected gel because long chains have a higher probability to bridge different globules and increase the number of interglobular association [34,40,41].…”

Section: Resultsmentioning

confidence: 99%

“…The synthesis and characterization of stereo-controlled PNIPAMs was described in Reference [34]. Table 1 lists the number-average molecular weight ( M n ), polydispersity (PDI), and tacticity of the investigated PNIPAMs.…”

Section: Methodsmentioning

confidence: 99%

“…Table 1 lists the number-average molecular weight ( M n ), polydispersity (PDI), and tacticity of the investigated PNIPAMs. The tacticity is defined as the percentage of the meso-diad content, which was determined by 1 H NMR [34]. Based on molecular weight, PNIPAMs are denoted as m and Hm series.…”

Section: Methodsmentioning

confidence: 99%

See 4 more Smart Citations

Rheological Study on the Thermoreversible Gelation of Stereo-Controlled Poly(N-Isopropylacrylamide) in an Imidazolium Ionic Liquid

2019

Self Cite

View full text Add to dashboard Cite

The thermoreversible sol-gel transition for an ionic liquid (IL) solution of isotactic-rich poly (N-isopropylacrylamides) (PNIPAMs) is investigated by rheological technique. The meso-diad content of PNIPAMs ranges between 47% and 79%, and molecular weight (Mn) is ~35,000 and ~70,000 g/mol for two series of samples. PNIPAMs are soluble in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide ([BMIM][TFSI]) at high temperatures but undergo a gelation with decreasing temperatures. The transition temperature determined from G’-G” crossover increases with isotacticity, consistent with the previous cloud-point result at the same scanning rate, indicating imide groups along the same side of backbones are prone to be aggregated for formation of a gel. The transition point based on Winter-Chambon criterion is on average higher than that of the G’-G” crossover method and is insensitive to tacticity and molecular weight, since it correlates with percolation of globules rather than the further formation of elastic network (G’ > G”). For the first time, the phase diagram composed of both G’-G” crossover points for gelation and cloud points is established in PNIPAM/IL mixtures. For low-Mn PNIPAMs, the crossover-point line intersects the cloud-point line. Hence, from solution to opaque gel, the sample will experience two different transitional phases, either clear gel or opaque sol. A clear gel is formed due to partial phase separation of isotactic segments that could act as junctions of network. However, when the partial phase separation is not faster than the formation of globules, an opaque sol will be formed. For high-Mn PNIPAMs, crossover points are below cloud points at all concentrations, so their gelation only follows the opaque sol route. Such phase diagram is attributed to the poorer solubility of high-Mn polymers for entropic reasons. The phase diagram composed of Winter-Chambon melting points, crossover points for melting, and clear points is similar with the gelation phase diagram, confirming the mechanism above.

show abstract

Section: Resultscontrasting

confidence: 62%

Section: Introductionsupporting

confidence: 72%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 3 more Smart Citations

Rheological Study on the Thermoreversible Gelation of Stereo-Controlled Poly(N-Isopropylacrylamide) in an Imidazolium Ionic Liquid

2019

Self Cite

View full text Add to dashboard Cite

show abstract

Dithioesters in RAFT Polymerization

Moad

2021

RAFT Polymerization

View full text Add to dashboard Cite

Lower Critical Solution Temperature in Poly(N‐Isopropylacrylamide): Comparison of Detection Methods and Molar Mass Distribution Influence

García‐Peñas

Biswas

Liang

et al. 2019

Macro Chemistry & Physics

Self Cite

View full text Add to dashboard Cite

Poly(N‐Isopropylacrylamide) has a broad potential range of biomedical applications owing to its lower critical solution temperature (LCST). This work tries to elucidate the real influence of several parameters on LCST by comparing homopolymers prepared by free radical polymerization and reversible addition–fragmentation chain transfer (RAFT) polymerization using conventional calorimetry, turbidimetry, and rheology as well as how three different methods can be used to detect the LCST. These methods are compared to gain a deeper understanding of the underlying processes and how they are related to molar mass and synthesis methods. The diverse interactions associated with the LCST transitions are more sensitive depending on the ratio defined between polymerization degrees and end‐group effects. Thus, the selection of a high sensitive method for LCST detection depends on the molecular features defined from the homopolymer. In addition, this work shows also the importance of the RAFT agent selected for the synthesis, which can modify substantially the LCST in comparison with other methods reported where the use of chemicals, complex processes, and costs considerably increase.

show abstract

Effect of tacticity and molecular weight on the rheological properties of poly(N-isopropylacrylamide) gels in benzyl alcohol

Cited by 11 publications

References 56 publications

Rheological Study on the Thermoreversible Gelation of Stereo-Controlled Poly(N-Isopropylacrylamide) in an Imidazolium Ionic Liquid

Rheological Study on the Thermoreversible Gelation of Stereo-Controlled Poly(N-Isopropylacrylamide) in an Imidazolium Ionic Liquid

Dithioesters in RAFT Polymerization

Lower Critical Solution Temperature in Poly(N‐Isopropylacrylamide): Comparison of Detection Methods and Molar Mass Distribution Influence

Contact Info

Product

Resources

About