Higher Lower Critical Solution Temperature Research Articles

Sustainable, super-stable thermochromic material by coupling hydroxypropyl cellulose and sodium carboxymethyl cellulose

Hydroxypropyl cellulose (HPC) is a green thermochromic material in energy-saving buildings, anti-counterfeiting, and data security fields. However, the high lower critical solution temperature (LCST) of HPC, around 42 °C (higher than the human thermal comfort temperature), limits its thermochromic sensitivity, poor stability, and short lifespan. Herein, we developed a durable, high-performance cellulose-based thermochromic composite with a lower LCST and easy preparation capability by combining HPC with sodium carboxymethyl cellulose (CMC). In such thermochromic cellulose, CMC constructs a hydrophilic skeleton to enable uniform dispersion of HPC, and functions as a stronger competitor to attract the water molecules compared to HPC, both of which trigger high thermochromic sensitivity and low LCST (just 32.5 °C) of our CMC/HPC. In addition, CMC/HPC shows superior stability, such as 100-day working capability and 60-time recyclability. This advancement marks a significant step forward in creating sustainable, efficient thermochromic materials, offering new opportunities for energy conservation in the building.

Synthesis and Thermo-Responsive Behavior of Poly(N-isopropylacrylamide)-b-Poly(N-vinylisobutyramide) Diblock Copolymer.

Thermo-responsive diblock copolymer, poly(N-isopropylacrylamide)-block-poly(N-vinylisobutyramide) was synthesized via switchable reversible addition-fragmentation chain transfer (RAFT) polymerization and its thermal transition behavior was studied. Poly(N-vinylisobutyramide) (PNVIBA), a structural isomer of poly(N-isopropylacrylamide) (PNIPAM) shows a thermo-response character but with a higher lower critical solution temperature (LCST) than PNIPAM. The chain extension of the PNVIBA block from the PNIPAM block proceeded in a controlled manner with a switchable chain transfer reagent, methyl 2-[methyl(4-pyridinyl)carbamothioylthio]propionate. In an aqueous solution, the diblock copolymer shows a thermo-responsive behavior but with a single LCST close to the LCST of PNVIBA, indicating that the interaction between the PNIPAM segment and the PNVIBA segment leads to cooperative aggregation during the self-assembly induced phase separation of the diblock copolymer in solution. Above the LCST of the PNIPAM block, the polymer chains begin to collapse, forming small aggregates, but further aggregation stumbled due to the PNVIBA segment of the diblock copolymer. However, as the temperature approached the LCST of the PNVIBA block, larger aggregates composed of clusters of small aggregates formed, resulting in an opaque solution.

Photothermal enhancement of reduced graphene oxide in hydroxypropyl cellulose for a smart-window application

The ability of hydroxypropyl cellulose (HPC)-based smart windows to dynamically regulate incident light and reduce energy consumption is of great interest. Although HPC is environmentally friendly due to its nontoxicity and biodegradability, commercial applications are limited due to its relatively high lower critical solution temperature (LCST). In this paper, reduced graphene oxide (rGO) was added to HPC solutions to enhance photothermal performance and access higher solution temperatures under sunlight illumination. For a 5-mL volume of HPC solution (0.5 wt%), each milliliter of rGO solution (0.1 mg/mL) increased the solution temperature by 3.13 °C. The tadpole-shaped fibers were hydrophilic below the LCST but became hydrophobic and tended to form net structures above the phase-change temperature. Water molecules were expelled from the web structure at the same time. Our work broadens the applications of HPC in smart windows.

A Study on the Dual Thermo- and pH-Responsive Behaviors of Well-Defined Star-like Block Copolymers Synthesize by Combining of RAFT Polymerization and Thiol-Ene Click Reaction.

A series of stimuli-responsive star-like block copolymers are synthesized via the combination of reversible addition, fragmentation chain transfer (RAFT) polymerization, and photo-initiated thiol-ene (PITE) click reaction. The controllable block ratio and block sequence, narrow distribution of molecular weight, and customized arm numbers of the star-shaped copolymers reveal the feasibility and benefits of combination of RAFT polymerization and PITE click reaction for synthesis of well-defined star-like (co)polymers. A clear insight into the relationship among the arm number, block sequence, and block ratio of the star-like block copolymers and their stimuli-responsive aggregation behavior was achieved via dynamic light scattering and UV-vis spectroscopy study. Notably, the star-like poly(acrylic acid)-b-poly(2-(dimethylamino) ethyl methacrylate) (star-PAA-b-PDMAEMA) shows higher lower critical solution temperature (LCST) compared to star-PDMAEMA-b-PAA with the same arm number and block ratio due to the inner charged PAA segments at pH > IEP. In addition, for star-like PAA-b-PDMAEMA, higher PAA content enhances the hydrophilicity of the polymer in basic solution and leads to the LCST increase, except for star-PAA1-b-PDMAEMA4 at pH = 9.0 (IEP). For star-PDMAEMA-b-PAA, the PAA content shows minimal effect on their LCSTs, except for the polymer in solution with pH = 9.5, which is far from their IEP. The star-like block copolymers with well-defined structure and tunable composition, especially the facile-controlled block sequence, bring us a challenging opportunity to control the stimuli-responsive properties of star-like block copolymers.

An AIE polymer prepared via aldehyde-hydrazine step polymerization and the application in Cu2+ and S2− detection

Herein we reported the synthesis of a novel amphiphilic AIE (aggregation-induced emission) polymer with salicylaldehyde azine (SA) moieties and PEG segments in the backbone via the aldehyde-hydrazine step polymerization. The polymer can self-assemble into stable micelles in water at ambient temperature and display intense orange fluorescence because of the aggregation of SA moieties in the core. Moreover, the polymer was found to be thermoresponsive with a relatively high LCST (lower critical solution temperature) and the LCST can be tuned via the chain length of PEG segments. The polymer micelles formed at ambient temperature can serve as a turn-off fluorescent probe for the selective detection of Cu2+ in aqueous media with a low detection limit of 53 nM. The fluorescence of polymer can be completely quenched by Cu2+ and the formed polymer-Cu2+ complex can be used as a turn-on fluorescent probe for the selective detection of S2− with a detection limit of 0.24 μM. The polymer is expected as a useful fluorescent probe for the selective detection of Cu2+ and S2− in environmental field.

Synthesis of thiol-terminated thermoresponsive polymers and their enhancement effect on optical limiting property of gold nanoparticles

Thermoresponsive thiol-terminated poly(N-isopropylacrylamide) (PNIPAM) and diblock poly(ethylene glycol)-b-poly(N-isopropylacrylamide) (PEG-b-PNIPAM) were synthesized through reversible addition-fragmentation chain transfer (RAFT) polymerization and aminolysis reaction. The lower critical solution temperature (LCST) of the polymers increases with the increase of PEG chain segment. Such polymers were used to modify gold nanoparticles (AuNPs) by Au–S bonds. The optical limiting property of the polymer-stabilized gold nanoparticles was investigated, and the results show that the thermoresponsive polymer-stabilized gold nanoparticles exhibit enhanced optical limiting effect relative to pristine AuNPs. The higher optical limiting energy threshold was observed for gold nanoparticles stabilized with polymers having higher LCST.

Smart carrier from electrospun core-shell thermo-sensitive ultrafine fibers for controlled drug release

In this study, electrospun core-shell thermo-sensitive (CSTS) ultrafine fibers were prepared successfully. The optimum structural polyethersulfone (PES) porous ultrafine fibers were chosen as core fabricated by electrospinning technology. In addition, in order to improve the lower critical solution temperature (LCST) of poly (N-isopropylacrylamide) (PNIPAm), acrylamide (Am) was chosen as the comonomer with excellent hydrophilicity and structural similarity to N-isopropylacrylamide. Thus, poly(N-isopropylacrylamide-co-acrylamide) P(NIPAm-co-Am) with higher LCST (LCST = 43 °C) was synthesized on the surface of PES fibers via radical copolymerization as shell. The introduction of the P(NIPAm-co-Am) influenced the morphology and performance of the PES ultrafine fibers significantly. Meanwhile, SEM, FTIR and XPS results all showed the P(NIPAm-co-Am) covered on the surface of PES fibers after polymerization for 4 h. Both the contact angle and shape change test indicated that the CSTS ultrafine fibers exhibited different wettability and area when the temperature was below and above the LCST due to the thermo-sensitive of P(NIPAm-co-Am) gels shell. Furthermore, curcumin was selected to use as drug model loaded in CSTS ultrafine fibers and the curcumin release behavior was tested to study the thermo-sensivity of CSTS ultrafine fibers. At 20 °C and 60 °C, the max curcumin release amount is w 33.21% and w 80.15%, respectively. The result directly demonstrated that CSTS ultrafine fibers had thermo-sensity as drug carrier. Finally, the cell culture studies showed that the prepared CSTS ultrafine fibers have a potential application in the biomedical fields.

Controlled Radical Copolymerization of Cinnamic Derivatives as Renewable Vinyl Monomers with Both Acrylic and Styrenic Substituents: Reactivity, Regioselectivity, Properties, and Functions.

A series of cinnamic monomers, which can be derived from naturally occurring phenylpropanoids, were radically copolymerized with vinyl monomers such as methyl acrylate (MA) and styrene (St). Although the monomer reactivity ratios were close to zero for all the cinnamic monomers, such as methyl cinnamate (CAMe), cinnamic acid (CA), N-isopropyl cinnamide (CNIPAm), cinnamaldehyde (CAld), and cinnamonitrile (CN), they were incorporated into the copolymers and significantly increased the glass transition temperatures despite the relatively low incorporation rates of up to 40 mol % due to their rigid 1,2-disubstituted structures. The regioselectivity of the radical copolymerization of CAMe was evaluated on the basis of the results of ruthenium-catalyzed atom transfer radical additions as model reactions. The obtained products suggest that the radicals of MA and St predominantly attack the vinyl carbon of the carbonyl side of CAMe and that the propagation of CAMe mainly occurs via the styrenic radical. The ruthenium-catalyzed living radical polymerization, nitroxide-mediated polymerization (NMP), and reversible addition-fragmentation chain transfer (RAFT) polymerization provided the copolymers with controlled molecular weights, narrow molecular weight distributions, and controlled comonomer compositions. The copolymers of N-isopropylacrylamide (NIPAM) and CNIPAm prepared via RAFT copolymerization showed thermoresponsivity with a lower critical solution temperature (LCST) that could be tuned by altering the comonomer incorporation and a higher LCST than the copolymers of NIPAM and St, which possessed similar molecular weights and similar NIPAM contents, due to the additional N-isopropylamide groups in the CNIPAm units compared to the St units.

Influence of Ethylene Glycol Methacrylate to the Hydration and Transition Behaviors of Thermo-Responsive Interpenetrating Polymeric Network Hydrogels.

The influence of ethylene glycol methacrylate (EGMA) to the hydration and transition behaviors of thermo-responsive interpenetrating polymeric network (IPN) hydrogels containing sodium alginate, N-isopropylacrylamide (NIPAAm), and EGMA were investigated. The molar ratios of NIPAAm and EGMA were varied from 20:0 to 19.5:0.5 and 18.5:1.5 in the thermo-responsive alginate-Ca2+/P(NIPAAm-co-EGMA) IPN hydrogels. Due to the more hydrophilicity and high flexibility of EGMA, the IPN hydrogels exhibited higher lower critical solution temperature (LCST) and lower glass transition temperature (Tg) when the ratio of EGMA increases. The swelling/deswelling kinetics of the IPN hydrogels could be controlled by adjusting the NIPAAm/EGMA molar ratio. A faster water uptake rate and a slower water loss rate could be realized by increase the amount of EGMA in the IPN hydrogel (the shrinking rate constant was decreased from 0.01207 to 0.01195 and 0.01055 with the changing of NIPAAm/EGMA ratio from 20:0, 19.5:0.5 to 18.5:1.5). By using 2-Isopropylthioxanthone (ITX) as a photo initiator, the obtained alginate-Ca2+/P(NIPAAm-co-EGMA360) IPN hydrogels were successfully immobilized on cotton fabrics. The surface and cross section of the hydrogel were probed by scanning electron microscopy (SEM). They all exhibited a porous structure, and the pore size was increased with the amount of EGMA. Moreover, the LCST values of the fabric-grafted hydrogels were close to those of the pure IPN hydrogels. Their thermal sensitivity remained unchanged. The cotton fabrics grafted with hydrogel turned out to be much softer with the continuous increase of EGMA amount. Therefore, compared with alginate-Ca2+/PNIPAAm hydrogel, alginate-Ca2+/P(NIPAAm-co-EGMA360) hydrogel is a more promising candidate for wound dressing in the field of biomedical textile.

Effect of polymer concentration on the lifetime and transmittance behavior of a self-oscillating polymer chain with a high lower critical solution temperature

In this study, we investigated the lifetime and self-oscillating behavior of a polymer chain with a high lower critical solution temperature (LCST). The polymer chain comprised 4-vinyl-4´-methyl-2,2´-bipyridinebis(2,2´-bipyridine)bis(hexafluorophosphate) ruthenium as catalyst for the Belousov–Zhabotinsky reaction and N-ethylacrylamide as the polymer main-chain with a high LCST when compared to N-isopropylacrylamide. We demonstrated that the self-oscillating behavior was significantly affected by the polymer concentration and measuring temperature. Moreover, we established that the lifetime of the transmittance self-oscillation can be predicted from the polymer concentration and measuring temperature.

Influence of the Belousov–Zhabotinsky substrate concentration on the lifetime and self-oscillating behavior of a polymer solution

In this study, we synthesized a self-oscillating polymer chain with N-ethylacrylamide (NEAAm) as the main-chain. This exhibits a higher lower critical solution temperature than an N-isopropylacrylamide main chain. We subsequently measured the transmittance self-oscillation of poly[NEAAm-co-Ru(bpy) 3 ] [Ru(bpy) 3 = 4-vinyl-4’-methyl-2,2’-bipyridinebis(2,2’ bipyridine)bis(hexafluorophosphate) ruthenium] solutions comprising three Belousov-Zhabotinsky (BZ) substrates (malonic acid, sodium bromate, and sulfuric acid), under stirring at constant temperature. The soluble-insoluble self-oscillation of the polymer solution originated from the different solubility of the Ru(bpy) 3 moiety as a catalyst of the BZ reaction in the reduced and oxidized states. We demonstrated that the self-oscillating behavior was significantly affected by the initial concentration of the sodium bromate. Moreover, we clarified that the lifetime of the transmittance self-oscillation can be predicted from the initial concentration of malonic acid.

Influence of cleavage of photosensitive group on thermally induced micellization and gelation of a doubly responsive diblock copolymer in aqueous solutions: A SANS study

In the present study, small-angle neutron scattering (SANS) was used to investigate the temperature and concentration dependence of micelle formation and growth of a thermo- and light-responsive hydrophilic block copolymer and the influence of removing photosensitive group. The water-soluble polymer poly(ethylene oxide)- b -poly(ethoxytri(ethylene glycol) acrylate- co - o -nitrobenzyl acrylate) (PEO- b -P(TEGEA- co -NBA) underwent sol-gel/gel-sol transitions in response to temperature changes in the range of 15–55 °C in a 25 wt% aqueous solution. The SANS data showed that individual chains existed at low temperatures and dilute solutions. Spherical micelles formed and packed into an ordered structure at elevated temperatures and high concentrations. Data fitting revealed that the micelle growth followed both micelle fusion and unimer insertion mechanisms after the critical micelle temperature was reached in moderately concentrated solutions whereas the fusion mechanism was dominant at higher temperatures. The UV exposure led to a 22% expansion in chain dimension at the unimer stage due to repulsive interactions between the ionized segments after the removal of the light sensitive group. The higher onset temperature of sol-gel transition after irradiation was mainly ascribed to the higher lower critical solution temperature (LCST). On the other hand, the lower gel-sol transition temperature upon UV exposure was due to the reduction in micelle volume fraction after the cleavage of o -nitrobenzyl group. These results correlated well with the dynamic rheological data. • SANS reveals the molecular mechanisms of polymer micellization and gelation. • The unimers stretch upon the removal of the light sensitive group. • The cleavage of the light sensitive group leads to a narrower gel zone. • The scattering data uncovers material distributions in micelles. • Micelle growth follows both micelle fusion and unimer insertion mechanisms.

Synthesis and characterization of temperature-sensitive cellulose-graft-poly(N-isopropylacrylamide) copolymers

A new series of cellulose-graft-poly(N-isopropylacrylamide) (cellulose-g-PNIPAM) copolymers were prepared by atom transfer radical polymerization (ATRP) of N-isopropylacrylamide monomers from a cellulose-based macro-initiator, which was homogeneously synthesized in an ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl). The composition of cellulose-g-PNIPAM copolymers could be adjusted by altering the feeding ratio and reaction time. The resultant copolymers with relatively high content of PNIPAM segments (molar substitution of PNIPAM ≥ 18.3) were soluble in water at room temperature. Aqueous solutions of cellulose-g-PNIPAM copolymers exhibited clear temperature-sensitive behavior, and their sol-to-gel phase transition properties were investigated by dynamic light scattering (DLS) and UV measurements. Compared with pure PNIPAM, the cellulose-g-PNIPAM copolymers possessed higher lower critical solution temperatures (LCST) in a range from 36.9 °C to 40.8 °C, which are close to normal human body temperature, and could be tuned by adjusting the content of PNIPAM segments in copolymers. Spherical structure of cellulose-g-PNIPAM copolymers formed at temperatures above LCST and its morphology was observed by TEM and SEM. These novel cellulose-g-PNIPAM copolymers may be attractive substrates for some biomedical applications, such as drug release and tissue engineering.

Preparation and characterization of CS-g-PNIPAAm microgels and application in a water vapour-permeable fabric

Chitosan-graft-poly(N-isopropylacrylamide) (CS-g-PNIPAAm) was synthesised using sonication with and without the crosslinker, N,N′-methylenebisacrylamide (MBA). FTIR, variable-temperature 1H NMR spectroscopy, atomic force microscopy, UV–vis spectrophotometry, differential scanning calorimetry, and dynamic light scattering were used to characterize the microgels’ chemical constituents, structures, morphologies, lower critical solution temperatures (LCSTs), and thermo- and pH-responsiveness. The chemical structures of the two CS-g-PNIPAAm materials were found to be similar and both exhibited dual responsiveness towards temperature and pH. The microgel containing MBA had a higher LCST, smaller diameter, and more compact structure, but exhibited opposite pH- and similar thermo-responsiveness. Although the structure of the microgel particles prepared without crosslinking was unstable, the stability of the crosslinked microgel particles enabled them to be finished onto fabric. Because the microgel prepared with MBA retains thermosensitivity, it can be used to impart controllable water vapour permeability properties. The incorporation of the MBA-crosslinked CS-g-PNIPAAm microgel particles in cotton fabric was accomplished by a simple pad-dry-cure procedure from an aqueous microparticle dispersion. The water vapour permeation of the finished fabric was measured at 25 and 40°C and 50 and 90% relative humidities. The finished fabric displayed an obviously high water vapour permeability at 40°C.

A Self-Oscillating Polymer Chain with High LCST

A novel self-oscillating polymer displaying a high lower critical solution temperature (LCST) was developed. The novel polymer chain underwent soluble-insoluble self-oscillation induced by a Belousov–Zhabotinsky reaction. The driving force of the self-oscillation was the differing solubility of the polymer chain in the reduced and oxidized states. The amplitude of self-oscillation was hardly affected by the concentration of the oxidant, sodium bromate. In addition, the period of the polymer solution could be controlled by careful selection of the concentration of the sodium bromate.

Synthesis and characterization of physically crosslinked N‐vinylcaprolactam, acrylic acid, methacrylic acid, and N,N‐dimethylacrylamide hydrogels

ABSTRACTPhysically crosslinked hydrogels based on N‐vinylcaprolactam/acrylic acid and N‐vinylcaprolactam/methacrylic acid were prepared via free radical polymerization. These temperature responsive hydrogels were characterized in terms of glass transition, phase separation temperature, potentiometric titration and swelling properties. Results showed that phase transition temperature was dependent on the pH value of the solution; increasing pH led to higher lower critical solution temperature (LCST) values which was related to the dissociative behaviors of the carboxylic group of MAc in the buffered solutions. Additionally, with the incorporation of N,N‐dimethylacrylamide into the system, cloud point measurements and MDSC showed an increased in the LCST. This increase was based on hydrophilicity, the hydrophilic–hydrophobic balance was disturbed, and consequently, the LCST behavior was shifted. The pKa of the copolymers ranged between 5.6 and 6.5, while for the terpolymers pKa ranged between 5.3 and 6. At high pH (>10), the COOH group is deprotonated and negatively charged (COO−), while at low pH (1–3) the carboxylic group remains protonated which results in hydrogen bonding between the hydroxyl groups (from NaOH) and the excess of HCl. These results correlate with swelling studies where above the pKa value the hydrogels dissolved rapidly compared to below pKa they did not dissolve at all. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1555–1564

Preparation and characterization of thermo‐sensitive poly(vinyl alcohol)‐based hydrogel as drug carrier

ABSTRACTPoly(vinyl alcohol)s (PVA) with high and low molecular weights were chemically modified by introducing acetaldehyde onto the polymer backbone to induce thermal‐responsive properties. The influence of both molecular weight ( ) and acetalization degree on the lower critical solution temperature (LCST) of thermo‐sensitive polymer was investigated. Moreover, a temperature responsive hydrogel was prepared by controlled cross‐linking of acetalized poly(vinyl alcohol) (APVA) and glutaraldehyde. As a model drug, ciprofloxacin was introduced into the prepared thermal sensitive hydrogel to reveal the drug loading and release behaviors. The structure, thermo‐sensitivity, swelling/deswelling kinetics, morphology, and drug loading/release behaviors were also investigated. The results indicated that the APVA polymer solution exhibited temperature responsivity, and APVA with high acetalization degree showed low LCST, whereas those with high PVAs showed high LCST. Meanwhile, morphology study was identical with the swelling/de‐swelling behavior. The loading and release of ciprofloxacin were controllable. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39720.

Unusual phase transition mechanism of poly(ethylene oxide) in an ionic liquid: opposite frequency shifts in C–H groups

The dynamic thermally reversible phase transition behaviour of poly(ethylene oxide) (PEO) in 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]) has been investigated by calorimetric measurements (DSC) and FT-IR, in combination with perturbation correlation moving window (PCMW) and two-dimensional correlation spectroscopy (2DCOS) for the first time. A relatively high lower critical solution temperature (LCST) was observed which is different from that of conventional thermo-sensitive polymers in aqueous solution. Four types of hydrogen bonds were found in this system, among which the type I (the hydrogen bonds between the unsaturated C–H on the imidazole ring and the oxygen atoms of PEO) and type II (the hydrogen bonds between the saturated C–H on the PEO backbone and the fluorine atoms of the IL anions) ones have a more predominant influence on the phase transition. Moreover, type I plays the predominant role in both the heating and cooling process. DSC revealed that the phase transition temperature of PEO–[EMIM][BF4] solutions decreases with the increasing concentration of PEO, as well as with a decreasing scanning rate. Through PCMW, the LCST was determined to be ca. 137 °C during heating and ca. 131 °C during cooling. Finally, 2DCOS was employed to elucidate the dynamic mechanism of PEO in [EMIM][BF4], which revealed hydrogen bond disruption, chain aggregation and exclusion of IL molecules. Solutions with a low PEO concentration tend to form loosely aggregated globules, compared to the more densely aggregated globules in samples with a high PEO concentration. Additionally, it is worth mentioning that several unusual and peculiar phenomena were also observed, such as opposite frequency shifts in C–H groups, a “tail-raising” phenomenon, critical PEO concentration for the phase transition temperature, and intersection of the frequency shift curves for samples with high concentrations of PEO during cooling.

Synthesis and properties of thermo-responsive macroporous PAM-co-PNIPAM microspheres

In this work, thermo-responsive macroporous Poly (acrylamide-co-N-isopropylacrylamide) (PAM-co-PNIPAM) microspheres with certain lower critical solution temperature (LCST) were synthesized by inverse suspension polymerization approach in the presence of toluene as porogenic agents. Various types of measurements, such as scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), Laser Particle Size Distribution Analyzer, N2 absorption analysis (BET) and Mercury Intrusion Porosimetry were conducted in characterizing PAM-co-PNIPAM particles. The results indicated that the obtained PAM-co-PNIPAM microspheres are perfect with porous structures which make the copolymer possess large surface area. And the size of the PAM-co-PNIPAM microspheres would change with the environmental temperature which is called thermo-responsive. Moreover, the copolymer synthesized from higher monomer weight ratio of AM/NIPAM has a relatively higher LCST.

Tuning the thermoresponsive properties of hyperbranched poly(ester amide)s based on diisopropanolamine and cyclic dicarboxylic anhydrides

AbstractA range of water‐soluble hyperbranched poly(ester amide)s has been synthesized with a view to studying their thermoresponsive behavior in water. Poly(ester amide)s with lower critical solution temperature (LCST) values around physiological temperatures are of interest for biological and medical applications, whereas poly(ester amide)s with high LCST values may be useful as kinetic hydrate inhibitors for high salinity produced fluids in the oil and gas industry. The LCST of these polymers was measured as the optical cloud point. The LCST can be tuned in various ways for these applications, for example, by varying the hydrophobicity of the groups on the cyclic anhydride monomer or by adjusting the hydrophilicity of the imine used to make the peripheral groups of the polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011