Research Article Self-Healing Hydrogels Based on

Research ArticleSelf-Healing Hydrogels Based on Carboxymethyl Chitosanand Acryloyl-6-aminocaproic Acid

Jiufang Duan

Institute of Material Science and Technology Beijing Forestry University Beijing 100083 China

Correspondence should be addressed to Jiufang Duan duanjiu99163com

Received 13 May 2015 Accepted 28 July 2015

Academic Editor Pasquale Longo

Copyright copy 2015 Jiufang DuanThis is an open access article distributed under the Creative Commons Attribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Once cracks have formed within hydrogel materials the integrity of the structure is signifcantly compromised regardless ofthe application Here we demonstrate cross-linked CMCS hydrogels can be engineered to exhibit self-healing under mildconditions CMCS hydrogels based onCMCS and acryloyl-6-aminocaproic acid (A6ACA)were synthesized by free radical aqueouscopolymerization using ammonium persulfate as initiator A series of hydrogels was synthesized varying the percentage of A6ACAThe hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR) techniques and their morphologies wereinvestigated by scanning electron microscope (SEM) images When the proportion of A6ACA was increased the compressivestrength stress and strain of hydrogels were increased The cross-linked hydrogel based on CMCS that can autonomously healbetween cut surfaces after 1 h was formed under mild conditions The increase of A6ACA content in the hydrogels will lead toincreased mechanical properties and mechanical healing efficiencies for highly cross-linked polymeric networks Hydrogen bondis the main reason for self-healing ability and the covalent cross-linkss and noncovalent cross-links both bear loads in the hyrogelPolymers with the ability to self-repair after sustaining damage could extend the lifetime of materials used in many applications

1 Introduction

Hydrogels consist of three-dimensional hydrophilic polymernetworks in which a large amount of water is interposedBecause of their unique properties a wide range of medicalpharmaceutical and prosthetic applications has been pro-posed for them [1ndash3] Carboxymethyl chitosan (CMCS) hasmany unique chemical physical and biological propertiessuch as low toxicity biocompatibility and good ability to formfilms fibers and hydrogels [1ndash3] Hydrogels with the ability torepair themselves after sustaining damage could extend thelifetime of materials used in many applications So far self-healing has been demonstrated in linear polymers host-guestpolymers [4 5] supramolecular networks [6 7] dendrimer-clay systems [8] metal ion-polymer systems [9] and multi-component systems [10ndash12] In recent years there has beenintense research into supramolecular network induced self-healing materials [13ndash15]

Supramolecular network is an effective way to pre-pare self-healing materials However the self-healing CMCS

hydrogels based on cross-linked network integrated by physi-cal or chemical methods have seldom been reported It wouldbe interesting to study the preparation of self-healing CMCShydrogels by an easy method Here we describe a strategy forintroducing physical and chemical cross-links into a syntheticCMCS network and demonstrate that such a network indeeddisplays self-healing properties

2 Experimental

21 Material and Methods Carboxymethyl chitosan amino-caproic acid acryloyl chloride and acrylamide ammoniumpersulfate andNN1015840-methylenebisacrylamide were of analyt-ical grade and used without further purification

IR spectra were recorded by FTIR (Nicolet iN10 ThermoFisher Scientific China) in the region of 400ndash4000 cmminus1Themorphological characterization of gel was performed withscanning electron microscopy (S-3400N HIACHI Japan)the gravimetric method was employed to measure theswelling ratios of the gels in distilled water at 25∘C After

Hindawi Publishing CorporationJournal of PolymersVolume 2015 Article ID 719529 6 pageshttpdxdoiorg1011552015719529

2 Journal of Polymers

HO

HO

N

C O

NH

NH

HH

CO

C O

CO

HN

COOH

OH

OH

CO

NH

Cut

C O

CO

Carboxymethyl chitosanPoly(AM-co-A6ACA)Covalent bondHydrogen bond

Self-healed

(CH2)5(CH2)5 (CH2)5

(CH2)5

ndashOH

ndashNH

ndashCONH2

ndashCOOH

Figure 1 Schematic illustration of the network in hydrogels

immersion in distilled water for about 48 hr to reach swellingequilibrium the gel samples were taken out and weighedafter removing the excess water on the surfaces Each datawas measured in three samples and the average value ofthree measurements was taken The equilibrium swellingratio (SR) was calculated as SR = 119882

119904119882119889 where 119882

119904is the

weight of the swollen gel and 119882119889is the weight of the gel

at the dry state mechanical property was measured usingan Instron 3365 Universal Testing Machine (Norwood MA)with the following parameters sampling rate 10000 ptssecbeam speed 10000mmmin full scale load range 01000 kNhumidity 25 and temperature 23∘C

22 Preparation of Hydrogel

221 Synthesis of A6ACA 01mol 6-aminocaproic acid and011mol NaOH were dissolved in 80mL deionized water inice bath under vigorous stirring To this 011mol acryloylchloride in 15mL tetrahydrofuran was added dropwise ThepHwasmaintained at 75 until the reactionwas completeThereaction mixture was then extracted with ethyl acetate Theclear aqueous layer was acidified to pH 30 and then extractedagain with ethyl acetate The organic layers were collectedcombined and dried over sodium sulfate The solution wasthen filtered concentrated and precipitated in petroleumether Further purification was achieved by repeated precipi-tation and the product was lyophilized [16]

222 Synthesis of Hydrogels Hydrogels were prepared byfree radical polymerization in aqueous solution contain-ing certain amounts of 86wt distilled water reactants(CMCS A6ACA = 1 1 mass ratio) 06 wt NN1015840-methyl-enebisacrylamide and 05 wt ammonium persulfate thatwere added to a three-neck reactor and dissolved in solutionpolymerized for 24 h at 37∘C

3 Results and Discussion

31 Preparation and Structure of Hydrogels During the freeradical polymerization the reactive double bonding groupson the surface of CMCS form highly branched polymer net-works which lead to CMCSs acting as multifunctional cross-links and bridge the adjacent CMCSs As a result the inter-twining of polymeric chainswas promoted and the hydrogen-bonding interaction between hydrophilic groups such asndashCOOH ndashCONH

2 ndashNH

2 and ndashOH among others was

strengthened (Figure 1)Thus the degree of cross-linking wasincreased fact that is extremely favorable to the improvementofmechanical propertiesThe cross-linked hydrogel based onCMCS that can autonomously heal between cut surfaces after1 h was formed under mild conditions (Figure 1) HoweverA6ACA was main reason for the efficient and robust healingof hydrogels the side chain was sufficiently long and flexibleand the network is sufficiently deformable to make the

Journal of Polymers 3

400900140019002400290034003900

(a)

(b)(c)(d)

(e)

Wavenumbers (cmminus1)

Figure 2 FTIR spectra of hydrogels with different A6ACA content(a) CMCS (b) A6ACA (c) 90wt (d) 80 wt (e) 50 wt

functional groups across the interface accessible to each otherbeyond the corrugation of the interface [15]

Figure 2 shows the FTIR spectra of the unmodified chitinand a series of products obtained by the grafting of CMCSwith A6ACA and AM As shown in Figure 2 the peaks forCMCS are at 1654 cmminus1 for the C=O bonds of the carboxylgroups After free radical copolymerization with A6ACA thespectra showed several new absorption bands in addition tothe original peaks of pure CMCS (Figures 2(c) 2(d) and2(e)) The new absorption band at 1715 cmminus1 was assigned tothe C=O stretching vibration of the amide group and thoseappearing at 1562 cmminus1 and 1404 cmminus1 were assigned to theasymmetric and symmetric stretching vibrations respec-tively [17] This clearly indicates that CMCS grating ofpolyA6ACA was successfully performed

32 Mechanical Properties All mechanical tests were per-formed in air at room temperature using a tensile machinewith a 100N load cellThe gel specimens weremade into cubeshape measuring 10 times 10 times 10mm3

We prepared hydrogels containing various proportions ofwater to study the best ratio of the hybrids which lead to thestretchable and strong properties When the proportion ofwater was increased the elongation at break and the strainof the hybrid hydrogel increased and then decreased from86wt (Figure 3) However the critical stretch at rupturereached a maximum at 86wt water When the water con-tent is relatively low the molecular chains will not effectivelystretch which result in the reactive group contact insuffi-ciently also when the water content is too high monomerfunctional groups will not collide effectively owing to lowerconcentration which result in low cross-linking density inboth cases Correspondingly the mechanical properties arepoor Unless otherwise stated the water content was fixed at86wt

One effectiveway to improve themechanical properties ofhydrogelswas increasing the cross-linking density [18]Whenthe proportion of A6ACA was increased the compressivestrength stress and strain were increased (Figures 4(a) and4(b)) With increasing amounts of A6ACA from 10wt

0

50

100

150

200

250

0 200 400 600 800 1000

Stra

in (k

Pa)

Stress ()

(a)(b)

(c)(d)

Figure 3 Effects of water content on mechanical properties ofhydrogels (water content (a) 80wt (b) 83wt (c) 86wt (d)90wt)

to 80wt the elongation at break and strain increasedfrom 47 to 101 and 76KPa to 850KPa respectively(Figure 4(a)) However the critical stretch at rupture reacheda maximum at 80wt A6ACAThe densities of noncovalentand covalent cross-links also strongly affect the mechani-cal behaviour of the hydrogels The increased compressivestrength strain and elongation at break were consistent withthe expected increases in the cross-linking densities in thethree-dimensional network structureThe hydrogen bondingin physical or chemical covalent cross-linked network wasstrengthened by more A6ACA because the A6ACA providesboth vinyl groups which can form covalent bonds andndashCONH

2 ndashNHndash and ndashCOOH groups which can form

hydrogen bonding [15] More A6ACA in matrix will corre-spondingly improve the mechanical properties of hydrogels

33 Absorbency of Hydrogels We prepared hydrogels con-taining various proportions of A6ACA to study the effectof A6ACA on the water absorbing capacity of hydrogelsAccording to Floryrsquos theory [19] cross-linking density is a keyfactor influencing the ability of water absorption hydrogelsAccording to Figure 5 there is a maximum swelling ratioat A6ACA 30wt amount Increasing the A6ACA amountfrom 10wt to 30wt the swelling ratio was increasedbecause the low content of A6ACA enhanced the hydrophil-icity of the hydrogel and caused a greater affinity for waterwhich was originated from the more hydrophilic groupsgenerated from A6ACA It can be observed that the capacityof water absorption by the gel decreases significantly withincreasing concentration of A6ACA from 30wt to 70wtThis is because the networks formed with high concentrationof A6ACA are strongly cross-linked and this fact reflectsin a smaller expansion of matrix and consequently smallervolume of water diffuses into the interior of the matrix [1920] Similar behavior was presented by Aouada et al [20] andPourjavadi et al [21]


0

100

200

300

400

500

600

700

800

900

0 20 40 60 80 100 120

Stre

ss (k

Pa)

Strain ()

(a)(b)(c)

(d)(e)

(a)

00

02

04

06

08

10

10 30 50 70 80 90

Com

pres

sive s

treng

th (M

Pa)

The content of acryloyl-6-aminocaproic acid ()

(b)

Figure 4 Effects of A6ACAcontent onmechanical properties of hydrogels (A6ACAcontent (a) 10 wt (b) 30wt (c) 50wt (d) 70wt(e) 80wt)

0

300

600

900

1200

1500

1800

2100

10 30 50 70

Swel

ling

ratio

()


Figure 5 The effect of A6ACA on the swelling ratio of hydrogels

34 The Self-Repairing Performance of Hydrogels Hydrogelswere synthesized using different concentrations of A6ACAwhich presents an important role in the self-healing charac-teristics of the hydrogel Hydrogels without A6ACA will loseself-repairing capacityThe increase of A6ACA concentrationin the CMCS hydrogels will lead to increased mechanicalproperties (stress increased from 76KPa to 632KPa andstrain increased from 47 to 71 (Figure 6)) which leadto both physical and chemical cross-links and mechanicalhealing efficiencies (stress healing efficiencies increased from19 to 48 and strain healing efficiencies increased from66 to 85 (Figure 6)) which lead to physical crosslinks [1522] Even at the highest A6ACA concentrations of 70wtthe mechanical performance in healed hydrogels is lowerthan in single hydrogels because in the hydrogel the covalentcross-links and noncovalent cross-links both bear loads andhydrogen bond is the main reason for self-healing abilityFailure in single hydrogels involves breakage of both covalent

bonds and intramolecular hydrogen bonds whereas failurein healed hydrogels involves only breakage of intermolecularhydrogen bonds across the interface which is a phenomenonthat has been observed in other supramolecular self-healingpolymer systems [22]

4 Conclusions

In summary we have demonstrated that self-healing canbe achieved in chemically cross-linked systems throughintroduction of pendant side chains offered by A6ACA Suchmaterials will increase the reliability and service life of ther-mosetting polymers used in a wide variety of applications

Conflict of Interests

The author declares that there is no conflict of interestsregarding the publication of this paper


0

10

20

30

40

50

60

70

80

0 10 20 30 40 50 60

Stre

ss (k

Pa)

Strain ()

Hydrogel 10Healed hydrogel

(a)

Stre

ss (k

Pa)

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60Strain ()


(b)

0

50

100

150

200

250

0 10 20 30 40 50 60 70

Stre

ss (k

Pa)

Strain ()


(c)

Stre

ss (k

Pa)

0

100

200

300

400

500

600

700

0 10 20 30 40 50 60 70 80Strain ()


(d)

Figure 6The self-healing properties of hydrogels (the content of A6ACA in the systemwas (a) 10wt (b) 30wt (c) 50wt (d) 70wt)

Acknowledgment

This paper is supported by the ldquoFundamental Research Fundsfor the Central Universitiesrdquo

References

[1] E Guibal ldquoInteractions of metal ions with chitosan-based sorb-ents a reviewrdquo Separation and Purification Technology vol 38no 1 pp 43ndash74 2004

[2] K Junka O Sundman J Salmi M Osterberg and J LaineldquoMultilayers of cellulose derivatives and chitosan on nanofibril-lated celluloserdquo Carbohydrate Polymers vol 108 no 1 pp 34ndash40 2014

[3] Y Xie H Qiao Z Su M Chen Q Ping and M SunldquoPEGylated carboxymethyl chitosancalcium phosphate hybridanionic nanoparticles mediated hTERT siRNA delivery foranticancer therapyrdquo Biomaterials vol 35 no 27 pp 7978ndash79912014

[4] N Masaki T Yoshinori Y Hiroyasu and H Akira ldquoRedox-responsive self-healing materials formed from host-guest poly-mersrdquo Nature Communications vol 2 article 511 6 pages 2011

[5] J F Duan X J Zhang J X Jiang et al ldquoThe synthesis of anovel cellulose physical gelrdquo Journal of Nanomaterials vol 2014Article ID 312696 6 pages 2014

[6] P Cordier F Tournilhac C Soulie-Ziakovic and L LeiblerldquoSelf-healing and thermoreversible rubber from supramolecu-lar assemblyrdquo Nature vol 451 no 7181 pp 977ndash980 2008

[7] M Burnworth L Tang J R Kumpfer et al ldquoOptically healablesupramolecular polymersrdquo Nature vol 472 no 7343 pp 334ndash337 2011

[8] Q GWang J L Mynar M Yoshida et al ldquoHigh-water-contentmouldable hydrogels by mixing clay and a dendritic molecularbinderrdquo Nature vol 463 no 7279 pp 339ndash343 2010

[9] N Holten-Andersen M J Harrington H Birkedal et al ldquopH-induced metal-ligand cross-links inspired by mussel yield self-healing polymer networks with near-covalent elastic modulirdquoProceedings of the National Academy of Sciences of the UnitedStates of America vol 108 no 7 pp 2651ndash2655 2011

[10] X Chen M A Dam K Ono et al ldquoA thermally re-mendablecross-linked polymeric materialrdquo Science vol 295 no 5560 pp1698ndash1702 2002

[11] B Ghosh andMW Urban ldquoSelf-repairing oxetane-substitutedchitosan polyurethane networksrdquo Science vol 323 no 5920 pp1458ndash1460 2009


[12] G V Kolmakov R Revanur R Tangirala et al ldquoUsing nano-particle-filled microcapsules for site-specific healing of dam-aged substrates creating a lsquorepair-and-gorsquo systemrdquo ACS Nanovol 4 no 2 pp 1115ndash1123 2010

[13] D LHan and L F Yan ldquoSupramolecular hydrogel of chitosan inthe presence of graphene oxide nanosheets as 2D cross-linkersrdquoACS Sustainable Chemistry amp Engineering vol 2 no 2 pp 296ndash300 2014

[14] M Vatankhah-Varnoosfaderani S Hashmi A Ghavami Nejadand F J Stadler ldquoRapid self-healing and triple stimuli respon-siveness of a supramolecular polymer gel based on boron-catechol interactions in a novel water-soluble mussel-inspiredcopolymerrdquo Polymer Chemistry vol 5 no 2 pp 512ndash523 2014

[15] A Phadke C Zhang B Arman et al ldquoRapid self-healinghydrogelsrdquo Proceedings of the National Academy of Sciences ofthe United States of America vol 109 no 12 pp 4383ndash43882012

[16] B P Lee P B Messersmith J N Israelachvili and J H WaiteldquoMussel-inspired adhesives and coatingsrdquo Annual Review ofMaterials Research vol 41 pp 99ndash132 2011

[17] H Kono and M Zakimi ldquoPreparation water absorbency andenzyme degradability of novel chitin- and cellulosechitin-based superabsorbent hydrogelsrdquo Journal of Applied PolymerScience vol 128 no 1 pp 572ndash581 2013

[18] K Kabiri H Omidian M J Zohuriaan-Mehr and S Doroudi-ani ldquoSuperabsorbent hydrogel composites and nanocompos-ites a reviewrdquo Polymer Composites vol 32 no 2 pp 277ndash2892011

[19] P J Flory ldquoPhase equilibria in polymer systemsrdquo in Principles ofPolymer Chemistry chapter 13 Cornell University Press IthacaNY USA 1953

[20] F A Aouada M R de Moura A F Rubira et al ldquoBirefringenthydrogels based on PAAm and lyotropic liquid crystal opticalmorphological and hydrophilic characterizationrdquo EuropeanPolymer Journal vol 42 no 10 pp 2781ndash2790 2006

[21] A Pourjavadi S H Barzegar and F Zeidabadi ldquoSynthesis andproperties of biodegradable hydrogels of 120581-carrageenan graftedacrylic acid-co-2-acrylamido-2-methylpropanesulfonic acid ascandidates for drug delivery systemsrdquo Reactive amp FunctionalPolymers vol 67 no 7 pp 644ndash654 2007

[22] S R White N R Sottos P H Geubelle et al ldquoAutonomichealing of polymer compositesrdquo Nature vol 409 no 6822 pp794ndash797 2001

Submit your manuscripts athttpwwwhindawicom

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

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NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


HO

HO

N

C O

NH

NH

HH

CO

C O

CO

HN

COOH

OH

OH

CO

NH

Cut

C O

CO

Carboxymethyl chitosanPoly(AM-co-A6ACA)Covalent bondHydrogen bond

Self-healed

(CH2)5(CH2)5 (CH2)5

(CH2)5

ndashOH

ndashNH

ndashCONH2

ndashCOOH

Figure 1 Schematic illustration of the network in hydrogels

immersion in distilled water for about 48 hr to reach swellingequilibrium the gel samples were taken out and weighedafter removing the excess water on the surfaces Each datawas measured in three samples and the average value ofthree measurements was taken The equilibrium swellingratio (SR) was calculated as SR = 119882

119904119882119889 where 119882

119904is the

weight of the swollen gel and 119882119889is the weight of the gel

at the dry state mechanical property was measured usingan Instron 3365 Universal Testing Machine (Norwood MA)with the following parameters sampling rate 10000 ptssecbeam speed 10000mmmin full scale load range 01000 kNhumidity 25 and temperature 23∘C

22 Preparation of Hydrogel

221 Synthesis of A6ACA 01mol 6-aminocaproic acid and011mol NaOH were dissolved in 80mL deionized water inice bath under vigorous stirring To this 011mol acryloylchloride in 15mL tetrahydrofuran was added dropwise ThepHwasmaintained at 75 until the reactionwas completeThereaction mixture was then extracted with ethyl acetate Theclear aqueous layer was acidified to pH 30 and then extractedagain with ethyl acetate The organic layers were collectedcombined and dried over sodium sulfate The solution wasthen filtered concentrated and precipitated in petroleumether Further purification was achieved by repeated precipi-tation and the product was lyophilized [16]

222 Synthesis of Hydrogels Hydrogels were prepared byfree radical polymerization in aqueous solution contain-ing certain amounts of 86wt distilled water reactants(CMCS A6ACA = 1 1 mass ratio) 06 wt NN1015840-methyl-enebisacrylamide and 05 wt ammonium persulfate thatwere added to a three-neck reactor and dissolved in solutionpolymerized for 24 h at 37∘C

3 Results and Discussion

31 Preparation and Structure of Hydrogels During the freeradical polymerization the reactive double bonding groupson the surface of CMCS form highly branched polymer net-works which lead to CMCSs acting as multifunctional cross-links and bridge the adjacent CMCSs As a result the inter-twining of polymeric chainswas promoted and the hydrogen-bonding interaction between hydrophilic groups such asndashCOOH ndashCONH

2 ndashNH

2 and ndashOH among others was

strengthened (Figure 1)Thus the degree of cross-linking wasincreased fact that is extremely favorable to the improvementofmechanical propertiesThe cross-linked hydrogel based onCMCS that can autonomously heal between cut surfaces after1 h was formed under mild conditions (Figure 1) HoweverA6ACA was main reason for the efficient and robust healingof hydrogels the side chain was sufficiently long and flexibleand the network is sufficiently deformable to make the


400900140019002400290034003900

(a)

(b)(c)(d)

(e)








0

50

100

150

200

250

0 200 400 600 800 1000

Stra

in (k

Pa)

Stress ()

(a)(b)

(c)(d)







0

100

200

300

400

500

600

700

800

900

0 20 40 60 80 100 120

Stre

ss (k

Pa)

Strain ()

(a)(b)(c)

(d)(e)

(a)

00

02

04

06

08

10

10 30 50 70 80 90

Com

pres

sive s

treng

th (M

Pa)


(b)


0

300

600

900

1200

1500

1800

2100

10 30 50 70

Swel

ling

ratio

()





4 Conclusions





0

10

20

30

40

50

60

70

80

0 10 20 30 40 50 60

Stre

ss (k

Pa)

Strain ()


(a)

Stre

ss (k

Pa)

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60Strain ()


(b)

0

50

100

150

200

250

0 10 20 30 40 50 60 70

Stre

ss (k

Pa)

Strain ()


(c)

Stre

ss (k

Pa)

0

100

200

300

400

500

600

700

0 10 20 30 40 50 60 70 80Strain ()


(d)


Acknowledgment


References































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




400900140019002400290034003900

(a)

(b)(c)(d)

(e)








0

50

100

150

200

250

0 200 400 600 800 1000

Stra

in (k

Pa)

Stress ()

(a)(b)

(c)(d)







0

100

200

300

400

500

600

700

800

900

0 20 40 60 80 100 120

Stre

ss (k

Pa)

Strain ()

(a)(b)(c)

(d)(e)

(a)

00

02

04

06

08

10

10 30 50 70 80 90

Com

pres

sive s

treng

th (M

Pa)


(b)


0

300

600

900

1200

1500

1800

2100

10 30 50 70

Swel

ling

ratio

()





4 Conclusions





0

10

20

30

40

50

60

70

80

0 10 20 30 40 50 60

Stre

ss (k

Pa)

Strain ()


(a)

Stre

ss (k

Pa)

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60Strain ()


(b)

0

50

100

150

200

250

0 10 20 30 40 50 60 70

Stre

ss (k

Pa)

Strain ()


(c)

Stre

ss (k

Pa)

0

100

200

300

400

500

600

700

0 10 20 30 40 50 60 70 80Strain ()


(d)


Acknowledgment


References































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0

100

200

300

400

500

600

700

800

900

0 20 40 60 80 100 120

Stre

ss (k

Pa)

Strain ()

(a)(b)(c)

(d)(e)

(a)

00

02

04

06

08

10

10 30 50 70 80 90

Com

pres

sive s

treng

th (M

Pa)


(b)


0

300

600

900

1200

1500

1800

2100

10 30 50 70

Swel

ling

ratio

()





4 Conclusions





0

10

20

30

40

50

60

70

80

0 10 20 30 40 50 60

Stre

ss (k

Pa)

Strain ()


(a)

Stre

ss (k

Pa)

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60Strain ()


(b)

0

50

100

150

200

250

0 10 20 30 40 50 60 70

Stre

ss (k

Pa)

Strain ()


(c)

Stre

ss (k

Pa)

0

100

200

300

400

500

600

700

0 10 20 30 40 50 60 70 80Strain ()


(d)


Acknowledgment


References































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0

10

20

30

40

50

60

70

80

0 10 20 30 40 50 60

Stre

ss (k

Pa)

Strain ()


(a)

Stre

ss (k

Pa)

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60Strain ()


(b)

0

50

100

150

200

250

0 10 20 30 40 50 60 70

Stre

ss (k

Pa)

Strain ()


(c)

Stre

ss (k

Pa)

0

100

200

300

400

500

600

700

0 10 20 30 40 50 60 70 80Strain ()


(d)


Acknowledgment


References































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Documents

Research Article Self-Healing Hydrogels Based on