Carboxymethyl chitosan has sensitive two-way CO2-responsive hydrophilic/hydrophobic feature

Shieh Y., Zeng Z., Cheng C.

Shieh Y., Hu F., Cheng C.

CO2-switchable multi-stimuli-responsive polymer nanoparticles (MSPNs), a combination of protonated poly(2-dimethylamino-ethyl methacrylate) (PDMAEMA) and hydrophobic poly(methyl methacrylate) (PMMA), were prepared by carbon-dioxide-assisted (CO2-assisted) emulsion polymerization. These MSPNs exhibited excellent thermal properties and unique temperature-/pH-responsive and CO2-/nitrogen-switchable (CO2-/N2-switchable) abilities, making them highly attractive multifunctional polymer nanoparticles with potential for many applications. Importantly, dispersion experiments and morphological studies clearly confirmed that these newly developed nanoparticles not only possess efficient, reversible CO2-/N2-switchable aggregation/redispersion ability, but also can remain in stable colloidal dispersion at low pH and promote rapid precipitation of nanoparticles at high pH. With simple preparation and high reproducibility, this approach provides a potentially novel pathway for the development of next-generation multifun...

Shieh Y., Lin Y., Cheng C.

Chitosan-g-poly[(2-dimethylamino)ethyl methacrylate] was investigated as a CO2-switchable emulsifier in this study. Poly(2-dimethylamino)ethyl methacrylate (PDMAEMA) was prepared by atom transfer radical polymerization followed by grafting to chitosan (CS). The CO2-responsiveness and reversible CO2-switchable temperature- and pH-sensitive behavior of PDMAEMA and CS-g-PDMAEMA were investigated as emulsifiers via simple CO2 and N2 bubbling. The lower critical solution temperatures (LCSTs) of PDMAEMA and CS-g-PDMAEMA aqueous solutions both increased as pH decreased to about pH 7.3, at which point the LCSTs disappeared. At elevated temperatures (e.g. 60°C), CO2 bubbling removed the turbidity in CS-g-PDMAEMA aqueous solution and N2 bubbling restored turbidity. The presence of CS-g-PDMAEMA in a two-phase solution of n-butanol/deionized water enabled the formation of a completely emulsified single phase after CO2 bubbling, which reverted to a two-phase solution on N2 bubbling. Overall, CS-g-PDMAEMA has potential as a CO2-switchable emulsifier.

Kalliola S., Repo E., Srivastava V., Heiskanen J.P., Sirviö J.A., Liimatainen H., Sillanpää M.

In environmental applications the applied materials are required to be non-toxic and biodegradable. Carboxymethyl chitosan nanoparticles cross-linked with Ca2+ ions (CMC-Ca) fulfill these requirements, and they are also renewable. These nanoparticles were applied to oil-spill treatment in our previous study and here we focused on enhancing their properties. It was found that while the divalent Ca2+ ions are crucial for the formation of the CMC-Ca, the attractive interaction between NH3+ and COO- groups contributed significantly to the formation and stability of the CMC-Ca. The stability decreased as a function of pH due to the deprotonation of the amino groups. Therefore, the nanoparticles were found to be fundamentally pH sensitive in solution, if the pH deviated from the pH (7-9) that was used in the synthesis of the nanoparticles. The pH sensitive CMC-Ca synthesized in pH 7 and 8 were most stable in the studied conditions and could find applications in oil-spill treatment or controlled-release of substances.

Alshamrani A.K., Vanderveen J.R., Jessop P.G.

CO2-responsive species in water interconvert between neutral and bicarbonate forms, but only if the species has appropriate basicity.

Darabi A., Jessop P.G., Cunningham M.F.

CO2is an ideal trigger for switchable or stimuli-responsive materials because it is benign, inexpensive, green, abundant, and does not accumulate in the system.

Kong X.

A novel method for simultaneously determining the degree of deacetylation (DD), the degree of substitution (DS) and the distribution fraction of –COONa (δ–COONa) or –COOH (δ–COOH) in carboxymethyl chitosan (CM-chitosan) was developed by potentiometric titration. The effect of precipitate on the third inflection point, a common problem in the previous method, was eliminated by integrated application of alkaline titration and acidic titration. Calculating formulas of DS, DD and δ–COONa considering both the residues (GlcN and GlcNAc) and the carboxymethyl forms (–COONa and –COOH) were proposed. CM-chitosan products in different forms were examined to prove the reliability of the method. The standard deviation of DS, DD and δ–COONa of Na salt CM-chitosan (n = 9) were 0.109, 3.51% and 4.30%, respectively. As CM-chitosan was confirmed by IR and 1H NMR to be N,O-CM-chitosan, the method is suitable for the parameter determination of N-, O- and N,O-CM-chitosan.

Han D., Tong X., Boissière O., Zhao Y.

By discovering that poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) in water can react with carbon dioxide (CO2) and have its lower critical solution temperature (LCST) reversibly tuned by passing CO2 and argon (Ar) through the solution, we describe a general strategy for imparting a CO2-switchable LCST or water solubility to polymers of broad interest like poly(N-isopropylacrylamide) (PNIPAM) and poly[2-(2-methoxyethoxy)ethyl methacrylate] (PMEO2MA). We show that by easy copolymerization incorporating DMAEMA as a CO2-responsive trigger into PNIPAM or PMEO2MA, their LCST can effectively be switched by the gases. Two examples of applications were further demonstrated: upon CO2 or Ar bubbling at a constant solution temperature, hydrogels could undergo a reversible volume transition and block copolymer micelles could be dissociated and reassembled. This study opens the door to a wide range of easily accessible CO2-switchable polymers, enabling the use of CO2 as an effective trigger for smart materials and devices.

Song Q., Zhang Z., Gao J., Ding C.

N-carboxymethyl chitosans (N-CMC) were synthesized from chitosan in water with chloroacetic acid instead of comparatively expensive glyoxylic acid. The optimal reaction conditions were 90°C and 4 h with a ratio of chloroacetic acid to chitosan 5 : 1(w/w). The degree of substitution of product exceeded 1.32. The N-carboxymethyl chitosans were characterized by XRD, FTIR, 1H-NMR, and the water solubility and isoelectric point of N-CMC with different degrees of substitution were determined. FTIR and 1H-NMR data has confirmed that the substitution reaction occurred on the amino groups. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Jayakumar R., Prabaharan M., Nair S.V., Tokura S., Tamura H., Selvamurugan N.

Chitin and chitosan are natural biopolymers that are non-toxic, biodegradable and biocompatible. In the last decade, chitin and chitosan derivatives have garnered significant interest in the biomedical and biopharmaceutical research fields with applications as biomaterials for tissue engineering and wound healing and as excipients for drug delivery. Introducing small chemical groups to the chitin or chitosan structure, such as alkyl or carboxymethyl groups, can drastically increase the solubility of chitin and chitosan at neutral and alkaline pH values without affecting their characteristics; substitution with carboxyl groups can yield polymers with polyampholytic properties. Carboxymethyl derivatives of chitin and chitosan have shown promise for adsorbing metal ions, as drug delivery systems, in wound healing, as anti-microbial agents, in tissue engineering, as components in cosmetics and food and for anti-tumor activities. This review will focus on the preparative methods and applications of carboxymethyl and succinyl derivatives of chitin and chitosan with particular emphasis on their uses as materials for biomedical applications.

Mourya V.K., N. Inamdara;Ashutosh Tiwari N.

Elsabee M.Z., Morsi R.E., Al-Sabagh A.M.

This review discusses the definition of surface active agents and specifically natural polymeric surface active agents. Chitosan by itself was found to have weak surface activity since it has no hydrophobic segments. Chemical modifications of chitosan could improve such surface activity. This is achieved by introducing hydrophobic substituents in its glucosidic group. Several examples of chitosan derivatives with surfactant activity have been surveyed. The surface active polymers form micelles and aggregates which have enormous importance in the entrapment of water-insoluble drugs and consequently applications in the controlled drug delivery and many biomedical fields. Chitosan also interacts with several substrates by electrostatic and hydrophobic interactions with considerable biomedical applications.

Lin C., Lin C.

The aim of this research was to develop pH-sensitive insulin-loaded NOCC (N,O-carboxymethyl chitosan) nanoparticles for the controlled release of insulin via the oral route. Thus, in this study, insulin-loaded NOCC nanoparticles were prepared by ionic gelation of NOCC with TPP (tripolyphosphate). NOCC nanoparticles were formed at conditions of 2 mg/ml of NOCC and 1 mg/ml of TPP. It was found that the encapsulation efficiency and process yield decreased with increasing NOCC to TPP weight ratio. Furthermore, the cumulative release of insulin from insulin-loaded NOCC nanoparticles decreased with decreasing NOCC-to-TPP weight ratio, but it increased with decreasing the initial concentration of insulin. The higher the pH of the phosphate buffered saline, the greater the amount of cumulative release of insulin-loaded NOCC nanoparticles, and thus they could protect insulin from acid.

Liu Y., Jessop P.G., Cunningham M., Eckert C.A., Liotta C.L.

Many industrial applications that rely on emulsions would benefit from an efficient, rapid method of breaking these emulsions at a specific desired stage. We report that long-chain alkyl amidine compounds can be reversibly transformed into charged surfactants by exposure to an atmosphere of carbon dioxide, thereby stabilizing water/alkane emulsions or, for the purpose of microsuspension polymerization, styrene-in-water emulsions. Bubbling nitrogen, argon, or air through the amidinium bicarbonate solutions at 65°C reverses the reaction, releasing carbon dioxide and breaking the emulsion. We also find that the neutral amidines function as switchable demulsifiers of an aqueous crude oil emulsion, enhancing their practical potential.

Shi X., Du Y., Yang J., Zhang B., Sun L.

The aim of this study was to evaluate the potential of carboxymethyl chitosan (CM-chitosan) nanoparticles as carriers for the anticancer drug, doxorubicin (DOX). Different kinds of CM-chitosan with various molecular weight (MW) and degree of substitution (DS) were employed to prepare nanoparticles through ionical gelification with calcium ions. Factors affecting nanoparticles formation in relation to MW and DS of CM-chitosan were discussed. By the way of dynamic light scattering (DLS), TEM, and atomic force microscopy (AFM), nanoparticles were shown to be around 200–300 nm and in a narrow distribution. FTIR revealed strong electrostatic interactions between carboxyl groups of CM-chitosan and calcium ions. DOX delivery was affected by the molecular structure of CM-chitosan. Increasing MWs of CM-chitosan from 4.50 to 38.9 kDa, DOX entrapment efficiency was enhanced from 10 to 40% and higher DS slightly improved the load of DOX. In vitro release studies showed an initial burst followed by an extended slow release. The DOX release rate was hindered by CM-chitosan with high MW and DS. These preliminary studies showed the feasibility of CM-chitosan nanoparticles to entrap DOX and the potential to deliver it as controlled release nanoparticles. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4689–4696, 2006

Cao H., He J.

Zhao Y., Hao H., Zhang G., Bi J., Yan S., Hong F., Hou H.

Li W., Xiang L., Liu Y., Sathishkumar G., He X., Wu H., Xiang Y., Xu K., Rao X., Kang E., Xu L.

Feng J., Tan Y., Sun L., Liang Q., Jiang T., Li Z.

Lin F., Jiang J.

Emulsions have extensive applications in food, cosmetics, and agriculture, while the requirements for emulsions differ in various fields. It is a challenge for one emulsion to satisfy multiple requirements in different applications. Herein, CO

Cai L., Wu J., Zhang M., Wang K., Yang Z.

Chen L., Xie Y., Chen X., Li H., Lu Y., Yu H., Zheng D.

O-carboxymethyl chitosan (O-CMC) is a chitosan derivative produced through the substitution of hydroxyl (-OH) functional groups in glucosamine units with carboxymethyl (-CH

Edo G.I., Yousif E., Al-Mashhadani M.H.

The second and most often utilized natural polymer is chitosan (CS), a naturally existing amino polysaccharide that is produced by deacetylating chitin. Numerous applications have been the subject of in-depth investigation due to its non-hazardous, biologically compatible, and biodegradable qualities. Chitosan's characteristics, such as mucoadhesion, improved permeability, controlled release of drugs, in situ gelation process, and antibacterial activity, depend on its amino (-NH

Ouyang P., Li Y., Wei W., Li Q., Liu J., MaYang, Li S., Zhou Y., Chen D., Geng Y., Huang X.

Diseases caused by viruses pose a significant risk to the health of aquatic animals, for which there are presently no efficacious remedies. Interferon (IFN) serving as an antiviral agent, is frequently employed in clinical settings. Due to the unique living conditions of aquatic animals, traditional injection of interferon is cumbersome, time-consuming and labor-intensive. This study aimed to prepare IFN microcapsules through emulsion technique by using resistant starch (RS) and carboxymethyl chitosan (CMCS). Optimization was achieved using the Box-Behnken design (BBD) response surface technique, followed by the creation of microcapsules through emulsification. With RS at a concentration of 1.27 %, a water‑oxygen ratio of 3.3:7.4, CaCl

Sun C., Ma H., Yu F., Xia S.

Emulsification viscosity reduction and subsequent demulsification are effective strategies to improve the utilization rate of heavy oil. However, traditional surfactants are challenged by unsatisfactory salt tolerance, inadequate stability in emulsification, difficulty in demulsification and pollution problem of oily wastewater discharge. To realize the feasibility and environment-friendliness of heavy oil utilization in the harsh reservoir environments, we designed a functional polymer and conducted a comprehensive evaluation using heavy oil samples from Chenping oil well in Shengli Oilfield. It was synthesized by grafting two hydrophobic monomers, lauryl methacrylate (LMA) and N, N–Diethylaminomethyl methacrylate (DEAEMA), onto the hydrophilia hydroxyethyl cellulose (HEC) by free–radical polymerization. The viscosity reduction rate can reach 99.57 % even under the high salinity of 26,050 mg/L. The stable oil–in–water (O/W) emulsion can be maintained for >48 h, satisfying the actual requirements for heavy oil recovery. Moreover, the emulsion can be completely demulsified in a CO2 atmosphere within 30 min, suggesting its satisfactory demulsification performance. Our study achieved the one–step transformation of heavy oil emulsion between emulsification and demulsification, which provides a green bio–based material and an ingenious strategy for enhanced oil recovery and other chemical engineering applications including oil/water separation.

Guo H., Shen H., Ma J., Wang P., Yao Z., Zhang W., Tan X., Chi B.

Wang K., An L., Lu G., Zhang J., Wang Z., Si M., Liu G., Zeng Y.

A series of novel thermo/pH/CO2-triple responsive homopolymers were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. These homopolymers contain ethoxy groups, and the end substituents are pyrrolidine, piperidine, N-methylpiperazine, morpholine and thiomorpholine, respectively. The effects of different heterocyclic substituents on the responsiveness of temperature, pH and CO2 were studied. For temperature-response, it was found that the lower critical solution temperature (LCST)-type cloud point (CP) temperature decreased as the number of carbon atoms increases, while the solubility of the polymers changed greatly with the introduction of oxygen, nitrogen and sulfur atoms. And the CP of the polymers can be adjusted by molecular weight, concentration and salt. Furthermore, some of these polymers present upper critical solution temperature (UCST) behavior in alcohols. For pH-response, the initial pH of the polymer solution is different, their critical pH changed accordingly, and is affected by temperature; in addition, changing the pH of solution can also affect the CP. For CO2-response, all of the polymers were completely soluble after pumping with CO2, and their LCST behavior recovered after N2 was pumped in, but there was a gap with the initial CP. The study of these properties reveals the influence of different heterocyclic substituents on the responsiveness of polymers, which is of great significance for understanding the stimulation response properties of polymers and provides ideas for the design of new stimuli-responsive polymers.

Liu Y., Liu Q.

As a promising method of carbon emission reduction, carbon capture, utilization and storage (CCUS) is an important technology to achieve carbon neutrality. CO 2 geological storage is an indispensable part of CCUS technology, and it is also the most effective measure for long-term storage of CO 2 . However, when the injected high-pressure CO 2 encounters formation water, the pH value of the system will turn down to about 3.0 Wellbore cement degradation would be a problem because the internal structure would become loose under such a strong acid environment for a long period, and can ultimately lead to gas leakage. In addition, the complex temperature and pressure changes caused by the injection of CO 2 in the underground would also lead to micro-annulus between cement-casing and cement-formation rock. Due to the existence of hydrodynamic drive and buoyancy, the escape of CO 2 is inevitable, thus an appropriate sealant is necessary for the remediation of CO 2 leakage pathways. Gel systems are widely used as sealants in the field of oil and gas industry. Polymer gel is a kind of organic gel that can be modified by changing synthesis methods and synthetic ingredient, for instance, CO 2 -responsive gels are prepared by introducing CO 2 -sensitive groups on the macromolecular chain. Inorganic gels such as silicate gels are also an ideal sealants thanks to their advance chemical stability and injectability. This paper mainly reviewed recent advances of three types of gel systems for CO 2 leakage remediation, namely CO 2 responsive gels, silicate gels and polymer gels. Gelation process and characteristic of gel systems were also discussed. Finally, based on current research advances and existing problems, future prospect of gel systems used for CO 2 leakage remediation were proposed. • Gel systems for CO 2 geological storage leakage remediation were reviewed systematically. • Mechanical strength, temperature resistance and injectivity of the gel system were proposed to be enhanced. • The importance of gel application of CO 2 -responsive gel was emphasized.

Li S., Meng H., Wang H., Vrouwenvelder J.S., Li Z.

High-performance nanofiltration (NF) membrane with super antifouling capability as well as reusability is highly desired in water treatment. A new antifouling strategy by a coating-decoating-recoating cycle was investigated for effective removal of fouling and restoring the original membrane performance. The functional membrane surface was fabricated by in-situ coating a 'green' and biodegradable carboxymethyl chitosan (CMCS) layer as physical barrier. The CMCS layer can be decoated and re-coated by simple procedures. Results showed that (i) the CMCS layer enhanced surface hydrophilicity, surface smoothness and fouling resistance of NF membrane, (ii) both the unfouled and fouled CMCS layer were easily decoated by the strong acid solution, (iii) the CMCS layer was easily re-coated by facile recoating and (iv) the water flux recovery ratio of membrane with coating layer was maintained more than 88.8% during fouling testing by natural organic matter (NOM) after four sequential cycles of coating, decoating and recoating process. The re-coated membrane exhibited stable, improved membrane operational and antifouling performance. The coating-decoating-recoating approach is proven to be low-cost and eco-friendly strategy for NOM fouling control on NF membrane in water treatment applications.

Alves D.C., de Farias B.S., Breslin C., Pinto L.A., Cadaval T.R.

There are an increasing number of carbon nanotubes (CNTs) based materials, which have been applied in environmental remediation treatment processes. Indeed, CNTs have outstanding properties, which can improve the electrical, mechanical and thermal properties of these composite materials. In addition to the nanoscale, which enhances the surface area of CNTs-based materials and, hence, the interaction with pollutants. Moreover, several CNTs-based materials have been synthesized with biopolymers, microbial biomass and food waste materials in order to improve their efficiency by increasing the amount and variety of functional groups through materials. In fact, the development of CNTs-based materials requires the elucidation of the interactions between CNTs and bio-based materials because they have an important role on materials properties and efficiency. Furthermore, this chapter will address the challenges regarding the possible ecological risks of CNTs. This chapter will also cover the different processes, which CNTs-based materials can be used for environmental remediation, such as membrane filtration, adsorption and photocatalytic degradation. Therefore, the current chapter will discuss and summarize the synthesis of CNTs-based materials, as well as environmental implications in order to overcome them and accomplish their use on a larger scale. Moreover, this chapter will explore the recent literature regarding the application of novel CNT-based materials in environmental remediation treatment processes.