"Smart" Materials Based on Cellulose: A Review of the Preparations, Properties, and Applications

Abstract

Cellulose is the most abundant biomass material in nature, and possesses some promising properties, such as mechanical robustness, hydrophilicity, biocompatibility, and biodegradability. Thus, cellulose has been widely applied in many fields. "Smart" materials based on cellulose have great advantages-especially their intelligent behaviors in reaction to environmental stimuli-and they can be applied to many circumstances, especially as biomaterials. This review aims to present the developments of "smart" materials based on cellulose in the last decade, including the preparations, properties, and applications of these materials. The preparations of "smart" materials based on cellulose by chemical modifications and physical incorporating/blending were reviewed. The responsiveness to pH, temperature, light, electricity, magnetic fields, and mechanical forces, etc. of these "smart" materials in their different forms such as copolymers, nanoparticles, gels, and membranes were also reviewed, and the applications as drug delivery systems, hydrogels, electronic active papers, sensors, shape memory materials and smart membranes, etc. were also described in this review.

Keywords: cellulose; drug delivery; smart materials; stimuli-responsive.

Figure 1

Molecular structure of cellulose.

Figure 2

Examples of “smart” materials based on cellulose and their possible applications.

Figure 3

Preparation strategies of “smart” materials based on cellulose.

Figure 4

Cylindrical-shaped PNIPAm-CMC full interpenetrating networks (IPN) hydrogels were prepared by the simultaneous radical crosslinking of CMC and PNIPAm polymer chains. The CMC/PNIPAm weight ratio was 5.0/95.0 and the hydrogels were prepared at 18 °C. PNIPAm: Poly(N-isopropylacrylamide); CMC: carboxymethyl cellulose. Reprinted with permission from [30]. Copyright 2010 Springer.

Figure 5

General mechanism for radical crosslinking of Na-Alg/CMC mixture in the presence of N,N′-methylene-bis-acrylamide (MBA). Reprinted with permission from [46]. Copyright 2006 Elsevier.

Figure 6

Synthesis route of microgels prepared from hydroxypropyl cellulose (HPC) [33].

Figure 7

Synthesis route of the poly(N,N-dimethyl aminoethyl methacrylate) (PDMAEMA) and poly(4-vinyl pyridine) (P4VP) grafted HPC via atom transfer radical polymerization (ATRP) [53,54].

Figure 8

Schematic diagram illustrating the processes for the preparation of the PNIPAm-g-HPC copolymers via ATRP of NIPAm from the alkyl bromide-functionalized HPC macroinitiator and the formation of stimuli-responsive hydrogels via crosslinking. Reprinted with permission from [55]. Copyright 2010 American Chemical Society.

Figure 9

Synthesis route of the thiolated HPC derivatives. Reprinted with permission from [58]. Copyright 2010 Royal Society of Chemistry.

Figure 10

Synthesis route of temperature-responsive hydrogels based on HEC. Reprinted with permission from [60]. Copyright 2010 Taylor & Francis.

Figure 11

Synthesis route of cellulose 2-[(4-methyl-2-oxo-2H-chromen-7-yl) oxy] acetates (3a-d) and cellulose 2-[(4-methyl-2-oxo-2H-chromen-7-yl) oxy] acetate [4-(N,N,N-trimethylamonium) chloride] butyrates (5a-d) via in situ activation of 2-[(4-methyl-2-oxo-2H-chromen-7-yl) oxy] acetic acid (2) and (3-carboxypropyl) trimethylammonium chloride (4) with N,N-carbonyldiimidazole (CDI) in DMAc/LiCl. Reprinted with permission from [67]. Copyright 2012 Springer.

Figure 12

Synthesis route of pH-responsive CNCs (carboxylated CNCs and amine-functionalized CNCs). Reprinted with permission from [72]. Copyright 2012 American Chemical Society.

Figure 13

Synthesis route of nanoparticles with photocleavable PS grafts. Reprinted with permission from [73]. Copyright 2012 Royal Society of Chemistry.

Figure 14

(a) Schematic of cellulose-PPy nanocomposite fabrication process; (b) Fabricated flexible humidity and temperature sensor. Reprinted with permission from [92]. Copyright 2010 Elsevier.

Figure 15

TEM images of dried dispersion of cellulose nanocrystals derived from (a) tunicate; (b) bacterial; (c) ramie; (d) sisal. Reprinted with permission from [69]. Copyright 2010 American Chemical Society.

Figure 16

Temperature dependence of ¹H NMR spectra of HPC-g-PDMAEMA solutions in D₂O at pH (a) 3.0; (b) 8.1; and (c) 12.3. Reprinted with permission from [53]. Copyright 2010 American Chemical Society.

Figure 17

Left: SEM images of freeze-dried gels; Right: (A) Equilibrium swelling degree (SWeq) vs. temperature; (B) Temperature of the volume phase transition T_v for HPC/PNIPAm-IPN having different composition. (a) PNIPAm; (b) HPC/PNIPAm interpenetrated network (composition of 53.7/46.3 wt/wt); (c) HPC. Reprinted with permission from [56]. Copyright 2004 Elsevier.

Figure 18

Schematic diagram showing ideal particle structure of drug carriers with temperature- and pH-responsive shells [108].

Figure 19

Partition coefficient of vitamin B12 into a composite membrane with 30 wt % of 1:0.4 particles (A) In 0.1 mM KCl at varied temperature; (B) In 0.15 M PBS with varied pH values at 28 °C; (C) Schematic illustration of the permeation model for a composite membrane containing temperature- and pH-responsive nanoparticles. Reprinted with permission from [84]. Copyright 2003 Elsevier.

Figure 20

Profiles of insulin delivery across a membrane in response to glucose steps (50 to 200 to 400 to 50 mg/dL) in pH 7.4 PBS (10 mM/0.15 M NaCl) at 37 °C. The membrane consisted of 1.5 mg of GOD/0.43 mg of catalase and 35 wt % of the nanoparticles with a NIPAm:MAA molar ratio of 1:1. Reprinted with permission from [85]. Copyright 2002 Elsevier.

Figure 21

(A) Effects of pH on the swelling behaviors of QC/CMC hydrogels in buffer solutions; (B) Swelling ratio of hydrogels in different salt solutions (0.01 M): NaCl, CaCl₂, and FeCl₃; and (C) Schematic illustrations of the structures of QC/CMC hydrogels: (a) Gel31; (b) Gel32; and (c) Gel13. Reprinted with permission from [44]. Copyright 2011 American Chemical Society.

Figure 22

Proposed rapidly switchable water-sensitive shape-memory mechanism for the cellulose nanowhiskers/PUs comprising a cellulose nanowhiskers percolation network in an elastomeric matrix. Reprinted with permission from [117]. Copyright 2012 Royal Society of Chemistry.

Figure 23

Deflection and back–forth swing images at 303 K under various applied voltages of the gel: (a) E = 0 V/mm; (b) E = 500 V/mm; (c) E = 525 V/mm; and (d) E = 550 V/mm. Note: The polarity of the electrode on the left and right hand sides are always GND and positive, respectively. Size of the gel sample: 16.5 mm of length, 1 mm of thickness, 3 mm of width, and 0.0309 g of weight. Reprinted with permission from [100]. Copyright 2012 Elsevier.

Figure 24

(A) Temperature-sensing characteristics at 70% RH; (B) Humidity sensing characteristics of cellulose-PPy nanocomposite; (C) Capacitance of cellulose-PPy nanocomposite sensor as a function of temperature and humidity. Reprinted with permission from [92]. Copyright 2010 Elsevier.

Figure 25

Various characteristic conformational states of PSBMA polymer chains in (a) DI water; and (b) NaCl solution; (c) Reversible electrolyte-responsive behavior of RC-g-PSBMA; (d) Dependence of rejection rates of BSA and NPs upon the concentration of NaCl solutions. Reprinted with permission from [161]. Copyright 2009 American Chemical Society.