Manipulating the Thermoresponsive Behavior of Poly(<i>N</i>-isopropylacrylamide). 1. On the Conformational Behavior of a Series of <i>N</i>-Isopropylacrylamide−Styrene Statistical Copolymers

Chee, Choong Kooi; Rimmer, Steve; Shaw, David; Soutar, Ian; Swanson, Linda

doi:10.1021/ma010360m

Cited by 69 publications

(127 citation statements)

References 30 publications

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“…Similar conformational transition in water with temperature increasing was monitored for more flexible and betterstudied PNIPAM using TROS and other complementary spectroscopic techniques, as quenching of fluorescence, excimer formation and fluorescence probe experiments, for acenaphthylene-labelled [11][12][13] polymer and for pyrene-labelled [14,15] polymer. It was shown, that local dynamics, quenching constant, probe solubilization and excimer formation are changing dramatically suggesting compactization of polymer chain in water at 32 8C.…”

Section: Resultsmentioning

confidence: 73%

“…This results were compared with those, obtained in methanol, were PNIPAM exist in coil state in the same experimental range of temperature. However, using more concentrated solutions as in present study, authors [11][12][13][14][15] presumed two-stage mechanism of PNIPAM behaviour nearly critical point. The first step involves intramolecular coil collapse.…”

Section: Resultsmentioning

confidence: 78%

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High Pressure Induced Coil‐Globule Transitions of Smart Polymers

Kirpach

Adolf

2006

Macromolecular Symposia

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Summary:In current work time-resolved optical spectroscopy (TROS) has been used to study coil-globule transitions monitored by the local segmental dynamics of anthracene labeled poly (N-isopropymethacrylamide), PNIPMAM as a function of pressure (0.1 MPa-200 MPa) over a temperature range of 283 K to 333 K. The positions of temperature-induced transition were observed to be independent on molecular weight of polymer at low pressures. The positions of pressure-induced transition were observed to be dependent on molecular weight of polymer at temperatures below LCST at atmospheric pressure. Double globule-coil-globule transition was observed to occur with pressure increasing at temperatures nearly above LCST. All these results along with values of intrinsic viscosity evaluated from values of correlation times measured for globules formed at different pressure/temperature conditions suggest the different mechanisms of compactisation governed by pressure and temperature and, correspondently, the different types of final structures. At low pressures with temperature increasing the compact, well-packed globules are forming via initial interactions between neighboring parts of polymer chain and further collapse. Relatively loosened particles are forming with pressurizing at low temperatures. Interaction between remote along the chain units takes part from the first stage of globule formation. And finally, rather solvated and irregularly twisted particles are forming at high pressure and high temperatures, i.e. at conditions, when both processes are involved.

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Section: Resultsmentioning

confidence: 73%

Section: Resultsmentioning

confidence: 78%

High Pressure Induced Coil‐Globule Transitions of Smart Polymers

Kirpach

Adolf

2006

Macromolecular Symposia

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“…, and 1.81×10 -3 s -1 at 65, 70, and 75°C, respectively, whereas for the conventional heating, it was determined to be 1.17×10 -5 s -1 at 75°C. The activation energy, E a , for the RAFT polymerization was estimated as 17.3 kJ/mol (Figure 1c), which is slightly higher than previously reported data [40]. The molecular weights also increased linearly with the monomer conversion to a dispersity (Đ) of approximately 1.34 (Figure 1d), indicating that the polymerization remained controlled.…”

Section: Cell Viability Assaymentioning

confidence: 55%

Microwave-assisted synthesis of thermo- and pH-responsive antitumor drug carrier through reversible addition–fragmentation chain transfer polymerization

Wang¹,

Zheng²,

Chang³

et al. 2017

Express Polym. Lett.

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Abstract. This paper reports the rapid synthesis of a dual-responsive copolymer through reversible addition-fragmentation chain transfer (RAFT) polymerization under microwave irradiation. Through use of 2-ethoxycarbonothioylthio acetic acid (ECTA) as a RAFT agent, the microwave-assisted polymerization rate of N-isopropylacrylamide (NIPAM) was approximately 150 times faster than that observed under conventional heating conditions, and the resulting homopolymer can be reactivated as a macroinitiator to produce poly(N-isopropylacrylamide-block-methacrylic acid) (PNIPAM-b-PMAA) block copolymers through a similar method. Research into the detailed polymerization kinetics of the PNIPAM and PNIPAM-b-PMAA revealed living characteristics that included a linear relationship between M n and conversion, controlled molecular weights, and a relatively narrow molecular weight distribution. The solution of the block copolymers in phosphate-buffered saline buffer displayed a phase transition at a lower critical solution temperature transition of 42°C, and altering the pH from 7 to 3.5 resulted in various degrees of polymer aggregation in the solution. Cisplatin was loaded to the polymeric carrier through a ligand exchange to form a macromolecular prodrug. The observed critical micelle concentration was 0.25 mg/mL. Overall, these polymers offer considerable potential for developing a new multifunctional drug delivery system.

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“…This explains the less pronounced drop of R h with increasing temperature for the PNIPAAMco-PAA system as compared with the PNIPAAM microgels. In addition, the PAA groups are suggested to act as "defects" in the PNIPAAM microgels causing a widening of the collapse region of the microgels [31][32][33][34].…”

Section: Resultsmentioning

confidence: 99%

Effects of addition of anionic and cationic surfactants to poly(N-isopropylacrylamide) microgels with and without acrylic acid groups

et al. 2012

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The interaction of the anionic surfactant sodium dodecyl sulfate (SDS) and the cationic surfactant hexadecyl trimethyl ammonium bromide with poly(N-isopropylacrylamide) (PNIPAAM) microgels with and without poly(acrylic acid) (PAA) was investigated by means of dynamic light scattering (DLS), zeta potential, and turbidimetry measurements. The DLS results show that the PNIPAAM microgels with PAA will contract when an anionic or cationic surfactant is added to the suspension, while the PNIPAAM microgels without PAA expand in the presence of an ionic surfactant. A collapse of the PNIPAAM microgels is observed when the temperature is increased. From the zeta potential measurements, it is observed that the charge density of PNIPAAM microgels in the presence of an ionic surfactant is significantly affected by temperature and the attachment of the negatively charged PAA groups. The turbidity measurements clearly indicate that the interaction between PNIPAAM and SDS is more pronounced than that of the cationic surfactant.

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Manipulating the Thermoresponsive Behavior of Poly(N-isopropylacrylamide). 1. On the Conformational Behavior of a Series of N-Isopropylacrylamide−Styrene Statistical Copolymers

Cited by 69 publications

References 30 publications

High Pressure Induced Coil‐Globule Transitions of Smart Polymers

High Pressure Induced Coil‐Globule Transitions of Smart Polymers

Microwave-assisted synthesis of thermo- and pH-responsive antitumor drug carrier through reversible addition–fragmentation chain transfer polymerization

Effects of addition of anionic and cationic surfactants to poly(N-isopropylacrylamide) microgels with and without acrylic acid groups

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