Mechanical Properties and Swelling Behav-ior of Acrylamide Hydrogels using Mont-morillonite and Kaolinite as Clays

Journal of Environmental Treatment Techniques

2019, Volume 7, Issue 2, Pages: 211-219

J. Environ. Treat. Tech.

ISSN: 2309-1185

Journal web link: http://www.jett.dormaj.com

Mechanical Properties and Swelling Behav-

ior of Acrylamide Hydrogels using Mont-

morillonite and Kaolinite as Clays

Farzaneh Sabbagh *, Nadia Mahmoudi Khatir , Azam Khodaeyan Karim , Amineh

Omidvar , Zahra Nazari , Reza Jaberi

- Bioprocess Engineering Department, Faculty of Chemical and Energy Engineering, Universiti Teknologi Malaysia, 81310

UTM, Johor, Malaysia

- Department of Biotechnology, Faculty of Biological Science, Alzahra University, Tehran, Iran

- Department of Food Science & Technology, Quchan Branch, Islamic Azad Univesity, Quchan, Iran

- Department of Chemistry, Payame Noor University (PNU)

- Food quality and Safety Research Group Food Science and Technology Research Institute ACECR Mashhad Branch

Mashhad, Iran

- Department of Food Science & Technology, Sabzevar Branch, Islamic Azad Univesity, Sabzevar, Iran

Received: 15/02/2019 Accepted: 30/04/2019 Published: 01/06/2019

Abstract

In this study in order to increase the release ability of acrylamide hydrogels, modified acrylamide-based hydrogel nano-

composites were synthesized. The aim of this research was to evaluate the swelling ratio of hydrogel with the best clay, to

reach the highest rate of swelling. To enhance the swelling ratio of hydrogels, the clays were applied in their structure.

Amongst the applied clays in the structure of the hydrogels, montmorillonite was found to be more effective than kaolinite.

Further using conventional techniques such as X-ray diffraction (XRD) and Energy Dispersive X-Ray (EDX) performed the

characterization of the clays, while the hydrogels were characterized by Fourier Transform Infrared Spectroscopy (FTIR),

Field Emission Scanning Electron Microscope (FESEM), and EDX. The XRD analysis of clays showed that there is a differ-

ent amount of carbon, oxygen, sodium, calcium, magnesium, aluminum, silicon, potassium and iron. The amount of oxygen

in montmorillonite was 42.12 however, the amount of oxygen in kaolinite was 2.01. The XRD pattern of montmorillonite

including a peak relevant to the basal dividing of (2θ = 7.83°) 11.28 Å was verified. In the acrylamide/montmorillonite hy-

drogels, this peak was shifted to a lower point of the angle, comparing to the basal spacing of (2θ = 6.40°) 13.78 Å and (2θ =

.24°) 14.11 Å. Such an increase in the basal spacing oblique that the monomer was inserted into the interlayer of the clay.

Keywords: Nanoparticle, NaCMC, Microstructure, Polymerization, Nanocomposite, Crosslinker

and very specific surface zone in their structure (5-8).

Clay is an organically tailored phyllosilicate, which is

derived from an organically occurring clay mineral. The

clay minerals are very effective in the polymer structure,

because they have small particle size and have intercala-

tion properties, and are hydrated layered aluminosilicate

with reactive -OH groups on their surface. The factors

such as pH, temperature and other environmental condi-

tions are able to impact on the hydrogels and the hydro-

gels can react to these factors as they are very powerful

materials (8,9). By locating of hydrophilic groups such as

amide, sulfonic acid, the hydroxyl group and carboxylic

acid in their structure, the hydrogels start to absorb a

large amount of water, they swell and can produce hy-

drophilic polymers (10-12). To improve the physical

properties of hydrogels, they can be added by novel ap-

plicable arrangements (13). Due to their stability under

violent conditions of procedure for health, they are very

exciting by locating of metal oxides such as MgO (14-

Introduction

Recently, the structure of hydrogels has been blended

by strengthening the nanostructures to polymerize a

nanocomposite hydrogel in order to make changes in

physical, mechanical and material properties (1). The

cross-linked structures in the three-dimensional systems,

provide the nanocomposite hydrogels which have simi-

larities with the layers in clay silicate (2). Some of the

useful applications of hydrogels including drug delivery

devices and wound dressing systems (3,4). The major

concerns on the hydrogels with clay-polymer structure

are focused on montmorillonite, laponite, and hy-

drotalcite as some improved factors. The reasons that the

clays are highly utilized for different medical applica-

tions is that they owe unique physicochemical qualities

Corresponding author: Farzaneh Sabbagh, Department

of Bioprocess Engineering, Faculty of Chemical Engi-

neering, Universiti Teknologi Malaysia, 81310. Email:

farzaneh2464@yahoo.com smfar-

zaneh2@live.utm.my. Telephone: 0060-177768087.

7). The MgO nanoparticles have various biomedical

advantages (18). The role of clays in pharmaceutical

products is excipient and active ingredients. Amongst all

and

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Journal of Environmental Treatment Techniques

2019, Volume 7, Issue 2, Pages: 211-219

the clays, montmorillonite has attracted more attention

due to having more capacity of cation exchange rather

than the rest of pharmaceutical silicates such as kaoline,

talc, and fibrous clay minerals (19). The composition of

clay/polymer composites has improved mechanical prop-

erties (20). These facts of interest along with the high

limit of interaction that is proposed by mineral particles

have been generally initiated to clarify novel systems of

controlled release yet sometimes it is necessary to modi-

fy polymeric material or clay minerals. Polyacrylamide is

a kind of pH-sensitive hydrogel (21,22).

edge (2θ) was in the range of 20 and 80 . An x-beam

diffraction amount of clay was carried out at 25 C with

Siemens. Diffractometer D5000 X-beam diffractometer

along with Cu (24).

2.4 FTIR Analysis

The FTIR spectrum of hydrogels was taken in the

range of 4000-370 cm as KBr pellet with the help of

FTIR (Nicolet. 670 FTIR, USA) were analyzed. Amount

of 4 mg of the dried specimens of hydrogels were weigh-

ing and blended with Potassium Bromide (25).

The aim of this study is to reach to the highest swell-

ing ratio in the hydrogels containing two different clays.

We are evaluating some characterizations and also the

highest swelling ratio between Montmorillonite and Kao-

linite and then apply one of them in the structure of hy-

drogel.

2.5 Hydrogel Nano Composites Microstructure

To consider the microstructure of hydrogels, Field

emission scanning electron microscope (FESEM) (35VP

Gemini Supra) was applied. This was done under vacu-

um condition and employing gold sputter coater Bio-Rad

Polaran Division (E6700, USA). The voltage of 10 kV

was carried out using the amplification of 3000× and

Experimental Methodologies

000×. To keep the samples pores wholesome for prepar-

.1 Materials

ing to image, all of them were lyophilized and were

placed in liquid (26).

Acrylamide (Aam) and MgO applied in this research

study were provided from Sigma-Aldrich Chemical

Company. N,N’-methylene bisacrylamide (MBA) as the

crosslinker, the activator N,N,N’, N’-tetramethyl eth-

ylenediamine (TEMED) and the initiator ammonium

persulfate (APS) were completely analytical grade and

were purchased from Sigma-Aldrich Chemical Compa-

ny. Deionized water was applied during the experiments

in the formulation of hydrogels in the swelling experi-

ments, Kaolin powder with 98% purity and montmorillo-

nite (MMT), with an average particle size of 1 μm was

used with no further modification. All the material was

obtained from Sigma-Aldrich Malaysia and supplemen-

tary chemicals and reagents applied were entirely analyt-

ical grade.

.6 Swelling Studies

Immersing the samples in distilled water conducted

to make them ready for swelling ratio analysis. Occa-

sionally, the weight of the swelling ratio was measured

and then computed by means of the following equation:

ꢀ

ꢁ ꢂ

ꢂ

Swelling ratio (%) = [

]ꢃꢄꢅꢆꢆ

(Equation 1)

The weight of the swollen gels is designed by Wt at time

t and W is the beginning weight of the samples (27).

Results and Discussion

.1 Reagents

.2 Formulation of Acrylamide/NaCMC/MgO Nano-

composites

Acrylamide/NaCMC/MgO nanocomposite was ac-

The presence of all of the elements that constitutes

the montmorillonite and kaolinite clay mineral may be

observed, indicating its effective incorporation (Table 1)

was determined by using elemental analysis, which re-

sulted in the unit cell formula. Apparently, the chemical

compositions breakdown of clay shows the main domi-

nant elements in the clay were (O=Oxygen),

cumulated by mixing 0.01 g MgO nanoparticles (<50nm)

and 0.01 g clay with the polymer matrix. First, MgO was

weighing for 0.01 g and poured into 2 ml of distilled

water at 80 °C under vigorous stirring.Acrylamide, am-

monium persulfate (APS), N, N, N’, N’-

tetramethylethylenediamine (TEMED), sodium carbox-

(C=Calcium), (Na= Sodium), (Mg= Magnesium), (Fe=

Iron), (Si=Silicon), (K=Potassium), (Al=Aluminum).

The EDX profile of montmorillonite and kaolinite (Fig-

ure 1 (a) and (b)) shows that the percentage of Si and Al

in the montmorillonite and kaolinite is 9.97% and

ymethylecellulose

(NaCMC),

N’-

methylenebisacrylamide (MBA), was added to the solu-

tion, after nearly 10 minutes. The whole duration of

polymerization of nano complex took about 40 mins

9.90%, and 17.18% and 5.96% respectively. Whereas

[

23].

the percentages of other metals like K, Na, Ca, Mg, O

and Fe is, 0.19%, 0, 0, 0, 2.01%, in kaolinite and 0.41%,

.3 XRD analysis

.32%, 0.49%, 0.79% and 42.12% in montmorillonite.

For the X-ray diffraction of Kaolinite and Montmo-

The major constituents of the clay are aluminum, silicon,

magnesium, iron, oxygen and calcium, which correspond

to its chemical formula.

rillonite, the clays were subjected to x-beam diffraction

XRD) Kα at 40keV and 40mA was applied with a step.

(

length of 0.05 and step time of 1s. The used diffraction

Table 1: EDX analysis of Kaolinite and Montmorillonite

Clays/ Elements

Kaolinite

(weight%)

Montmorillonite (weight%)

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2019, Volume 7, Issue 2, Pages: 211-219

The representing of O and Si components, coming

absolutely from the clay mineral, suggests that good

element dispersion occurred in the clay matrix (Figure 1).

So as to consider the composition of montmorillonite and

kaolinite, XRD test was accomplished (Figure 1). The

crystallinity changes of samples with clays were consid-

ered to have a better understanding of hydrogel structural

stability and network.

The large surface area of Kaolinite and montmorillo-

nite and/or their extensive pharmaceutical application are

the main reasons to choose them. The properties of such

different clays are related to their composition and struc-

ture (Figure 2). The montmorillonite clays are 2:1 phyl-

losilicates stacked single sheets of tetrahedral silica on

top of a single sheet of octahedral alumina however,

kaolinite consists of 1:1 (28). The way that the layers are

stacked on each other detects the differences in the kaolin

minerals. The interlayer in montmorillonite is not only

expansible, but it is also hydrated; That is the reason,

they are called to as "swelling clays" (29).

the interlayer space of smectites, by revealing changes in

the basal spacing of the clay minerals (30). The XRD

pattern of kaolinite is presented in figure 3(a) and the

XRD pattern of montmorillonite is presented in figure

3(b).

The diffraction pattern of montmorillonite including

a peak relevant to the basal dividing of (2θ = 7.83°)

11.28 Å was verified. In the acrylamide/montmorillonite

hydrogels, this peak was shifted to a lower point of the

angle, comparing to the basal spacing of (2θ = 6.40°)

13.78 Å and (2θ = 6.24°) 14.11 Å. Such an increase in

the basal spacing oblique that the monomer was inserted

into the interlayer of the clay. This is due to the polymer-

ization of acrylamide monomer to polyacrylamide matrix

that gave a contraction between layers of the montmoril-

lonite (31). A flattened conformation was adopted be-

tween the layers of the clay in the polymer. It is conclud-

ed that in composite hydrogels the clay minerals were

intercalated but not exfoliated and authoritatively dis-

seminated in the matrix. Small molecules (kaolinite)

were weakly bound to the clay mineral and no significant

changes in the basal spacing of the complexes were ob-

served after desorption, whereas for promethazine im-

portant modifications in the X-ray were reported (32).

.2 XRD pattern of Clays

The X-ray diffraction performed for the clays are

presented in Figure.3.X-ray diffraction was a useful tool

to test the possible orientation and penetration of clays in

(a)

(b)

Figure 1: Energy Dispersive X-Ray (EDX) spectrum of clay Montmorillonite(a) and Kaolinite (b)

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2019, Volume 7, Issue 2, Pages: 211-219

(a)

Montmorillonite structure (NA,CA)₀_.₃₃(AL,MG) (SI O )

(b)

Kaolinite structure Al Si O (OH )

Figure 2: Chemical structure of (a) Montmorillonite and (b) Kaolinite

.3 Polymerization

The polymerization of acrylamide hydrogels is

polymer/clay systems could have a tendency to

produce disordered phases as nematic or isotropic,

an increase of polymer chain length and/or organ

clay content leads to the creation of ordered phases

(crystal, smectic or columnar) (33).

happening in the presence of smaller amount of

bisacrylamide. Bisacrylamide essentially is linked to

two acrylamide molecules by a methylene group,

and is applied as crosslinking agent. A second site

to extend the chain is introduced due to polymeriza-

tion of acrylamide monomer in the head to tail order

and producing bisacrylamide molecules into long

chains. The polymerization of acrylamide monomer

is free radical’s catalysis, and by the addition of

TEMED and APS is initiated. The TEMED role in

the matrix is catalyzer of the decomposition of per-

sulphate ion and presents free radical. Hydrogel

composites were shaped by some interaction and

conglomeration with acrylamide in montmorillonite

interlayer gallery. Acrylamide/montmorillonite

composite hydrogel and Acrylamide/ kaolinite com-

posite hydrogel were the result of free radical

polymerization in distilled water containing of clay

in optimized ratio of acrylamide to clay (6:1%,

w/w), APS and TEMED were added as the initiator

and accelerator, respectively. The content of the

clay is very important. At lower contents of clay, the

3.4 Swelling ratio study

According to the outcomes, the specifications of

acrylamide hydrogel were encouragingly trans-

formed by incorporating with clays. The two men-

tioned clays were applied in the hydrogels and were

placed in distilled water to determine the swelling

ratio (Figure 4). By comparing these samples,

Montmorillonite had the greatest swelling ratio

rather than kaolinite.

In Figure 4, the swelling ratio of the hydrogel in

distilled water is presented and by NaCMC addition,

the quantity of swelling was found to be increased

to a greater level. On the other hand, the presence of

multitude carboxylic acid groups in its structure is

very effective. The presence of hydrophilic chains

on the polymeric chains (–COOCH Na) and (–OH)

and hydration of functional groups was responsible

for the swelling of the hydrogels.

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2019, Volume 7, Issue 2, Pages: 211-219

350

300

250

200

150

100

-Theta-Scale

Kaolinite (a)

-Theta-Scale

Montmorillonite (b)

Figure 3: XRD pattern of Kaolinite (a) and Montmorillonite (b)

enhanced owing to the aggregate permeability of hydro-

gels that give them the ability to release the trapped

drugs easier. However, it is seen that acrylamide hydro-

gels in establishment with montmorillonite swells faster

than the hydrogels incorporation with kaolinite. This fact

could be explained by the presence of strongly hydro-

philic clay that attracts water at the beginning of swelling

much faster than the kaolinite with different structure

rather than montmorillonite (35).

.5 Characterization of Modified Acrylamide Based-

Hydrogel Nanocomposites

.5.1 FTIR Characterization

The Figure 5 represents the synthesis of acrylamide-

based hydrogels obtained from the FTIR spectra. The

peak for ester groups was found around 703. The peak of

Figure 4: Swelling ratio of Kaolinite and Montmorillonite clays

using in the acrylamide-based hydrogels

368 relates to silicon capacity and the peak of 1650 cm

According to our previous reports (34), by expanding

the swelling ability of hydrogels, the drug release and

loading components within the hydrogel network are

is a result of amide-I of acrylamide units (36). The peak

2929 cm is for presence of C–N and C–H extending

groups, separately, further affirming the trend of the

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2019, Volume 7, Issue 2, Pages: 211-219

amide group. The extending of –OH gatherings result in

with minor modification. FESEM was performed in or-

der to assess the surface characterization of hydrogels

(38). Polyacrylamide containing Kaolin and montmoril-

lonite microparticles have macro porous structure with

average diameter of pore size less than 1 µm. MgO na-

noparticles organized the initial burst release organized

through modification of polymeric complex and by af-

fecting the release mechanism (39,40). The FESEM im-

ages magnifications were undergone at 2.0K×. Apparent-

ly, stacking nanoparticles had changed the surface mor-

phology of the clear hydrogel. This shows the arrange-

ment of nanoparticles in the system of the clear hydrogel,

while the clear hydrogel uncovered clear systems through

the gel association. Also, it is clear that nanofillers pro-

duce a same type of structure once integrated into the

blank matrix, which was more evident in the magnetic

type of nanocomposites. Making of nanoparticles inside

the hydrogel system brings about moving the porosity of

hydrogels. It can be seen that the nanoparticles have

effectively unbroken apportion through the hydrogel

organizes as demonstrated in Figure.7. The EDX range

moreover supports the arrangement of metal nanoparti-

cles in the hydrogels (41).

–

–1

peak 3421 cm . The peak at 1023 cm advocated –CH–

–

O–CH– extending. The peak is seen at 1650 cm was a

direct result of the amide-I band of the amide group of

polyacrylamide (>C = O stretching vibration frequency).

−1

The amide-I band was relocated from 1661cm , in the

−1

cross-connected polyacrylamide, to 1650cm .The peaks

−1

at 1023 cm in the FTIR range is normal for skeletal

vibration including the extending of C–O bonds in anhy-

–

drous glucose units. The peaks at 2929 cm indicated C–

H stretching of – CH groups. This infers that due to the

less steric restriction of the hydroxyl group, the hydroxyl

group of acrylamide is the favored site for the response

with the crosslinker and the joining of acrylamide (37).

.5.2 FESEM, EDX analysis

The dynamic swelling behavior of hydrogels depends

on the relative contribution of penetrant diffusion and

relaxation of crosslinked polymer chains. It was until

affirmation the outcome of nanoparticles on the micro-

structure of hydrogel, FESEM/EDX of the clear hydrogel

and the nanoparticles-stacked hydrogels were considered

as demonstrated in Figure 6. Field Emission Scanning

Electron Microscopy (FESEM) analysis was carried out

Wavenumber(cm )

Figure 5: FTIR spectra for acrylamide-based hydrogels

Figure 6: FESEM image of MgO/Acrylamide/NaCMC

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2019, Volume 7, Issue 2, Pages: 211-219

Figure 7: EDX of MgO/Acrylamide/NaCMC hydrogels

Conclusion

References

[1] Gholizadeh, H., Cheng, S., Pozzoli, M., Messerotti,

E., Traini, D., Young, P., Kourmatzis, A., Ong, HX.

Smart thermosensitive chitosan hydrogel for nasal

delivery of ibuprofen to treat neurological disorders.

Expert opinion on drug delivery, 2019.

[2] Ruskowitz, ER., Comerford, MP., Badeau, BA.,

DeForest, CA. Logical stimuli-triggered delivery of

small molecules from hydrogel biomaterials. Bio-

materials science, 2019.7(2): p.542-546.

The layered silicate materials such as montmorillo-

nite, have drawn a great deal of attention because of its

ability to release drugs in a controlled mode, ultimately

leading to high value of drug. Polyacryla-

mide/montmorillonite and polyacrylamide/kaolinite

composites were obtained by polymerization. Network

parameters and Swelling behavior of hydrogels were

studied. The study results indicated that the montmoril-

lonite is the best clay to be applied in the hydrogel

among the clays, due to its highest swelling ratio. Addi-

tion of nanoparticles changed the water-uptake in hydro-

gels by direct water adsorption (at the water interface),

and changing the network density (by adding physical

crosslink points to the existing chemical crosslinks). By

adding the MgO to the monomer system the greater

swelling capacity of the MgO hydrogels can be attributed

to the presence of MgO nanoparticles with different sur-

face charges, size, and morphology. The MgO nanoparti-

cles caused in the dispersion of more water molecules to

equilibrate the buildup ion osmotic pressure, which re-

sulted in swelling. As a future recommendation, it can be

suggested to apply two clays with the highest abilities in

the swelling and thus to reach to highest amount of re-

lease in the drug delivery systems.

[3] Jämstorp Berg, E. Diffusion controlled drug release

from slurry formed, porous, organic and clay-derived

pellets (Doctoral dissertation, Acta Universitatis

Upsaliensis).

[4] Nesrinne, S., Djamel, A. Synthesis, characterization

and rheological behavior of pH sensitive poly

(acrylamide-co-acrylic acid) hydrogels. Arabian

Journal of Chemistry, 2017. 10(4): p. 539-547.

[5] Duncan, J., MacDonald, JF., Hanna, JV., Shirosaki,

Y., Hayakawa, S., Osaka, A., Skakle, JM., Gibson,

IR. The role of the chemical composition of monetite

on the synthesis and properties of α-tricalcium phos-

phate. Materials Science and Engineering: C,

2014.1(34): p.123-129.

[6] Dragan, ES., Lazar, MM., Dinu, MV., Doroftei, F.

Macroporous composite IPN hydrogels based on

poly (acrylamide) and chitosan with tuned swelling

and sorption of cationic dyes. Chemical engineering

journal, 2012. 15(204): p. 198-209.

Conflicts of interest

The authors have no conflicts of interest.

[

7] Dinu, MV., Perju, MM., Drăgan, ES. Composite IPN

ionic hydrogels based on polyacrylamide and dextran

sulfate. Reactive and Functional Polymers, 2011.

Ethical issue

Authors are aware of, and have complied with the

best practice in publication ethics specifically with regard

to authorship, dual submission, and manipulation of fig-

ures, competing interests and compliance with policies

on research ethics. Authors have adhered to publication

requirements that this submitted work is original and has

not been published elsewhere in any form of language.

1(8): p. 881-890.

8] Guiseppi-Elie, A., Koch, L., Finley, SH., Wnek, GE.

The effect of temperature on the impedimetric re-

sponse of bioreceptor hosting hydrogels. Biosensors

and Bioelectronics, 2011. 26(5): p. 2275-2280.

9] Kevadiya, BD., Pawar, RR., Rajkumar, S., Jog, R.,

Baravalia, YK., Jivrajani, H., Chotai, N., Sheth, NR.,

Bajaj, HC. pH responsive MMT/acrylamide super

composite hydrogel: characterization, anticancer

drug reservoir and controlled release property.

Biochem Biophys, 2013. 1(3):p. 43-60.

Competing interests

The authors wish to declare that there is no conflict

of interest in this research work.

[

10] Leal, D., De Borggraeve, W., Encinas, MV., Matsu-

hiro, B., Müller, R. Preparation and characterization

of hydrogels based on homopolymeric fractions of

sodium alginate and PNIPAAm. Carbohydrate poly-

mers, 2013. 92(1):p.157-166.

Authors’ contribution

All the authors of this study have completely

contributed to the data collection, data analyses and

manuscript writing.

11] Mittal, H., Jindal, R., Kaith, BS., Maity, A., Ray,

SS. Flocculation and adsorption properties of biode-

217

Journal of Environmental Treatment Techniques

2019, Volume 7, Issue 2, Pages: 211-219

gradable gum-ghatti-grafted poly (acrylamide-co-

methacrylic acid) hydrogels. Carbohydrate polymers,

of Inorganic and Organometallic Polymers and

Materials, 2017. 27(5):p.1439-1449.

015. 22(115): p.617-628.

[26] Yang, X., Guo, L., Fan, Y., Zhang, X. Preparation

and characterization of macromolecule cross-linked

collagen hydrogels for chondrocyte delivery. Interna-

tional journal of biological macromolecules, 2013.

1(61): p.487-493.

[

12] Singh, B., Sharma, V. Influence of polymer network

parameters of tragacanth gum-based pH responsive

hydrogels on drug delivery. Carbohydrate polymers,

014. 30(101): p.928-940.

13] Huh, HW., Zhao, L., Kim, SY. Biomineralized bio-

mimetic organic/inorganic hybrid hydrogels based on

hyaluronic acid and poloxamer. Carbohydrate poly-

mers, 2015. 1(126): p.130-140.

14] Samanta, HS., Ray, SK. Synthesis, characterization,

swelling and drug release behavior of semi-

interpenetrating network hydrogels of sodium

alginate and polyacrylamide. Carbohydrate polymers,

[27] Akalp, U., Chu, S., Skaalure, SC., Bryant, SJ.,

Doostan, A., Vernerey, FJ. Determination of the pol-

ymer-solvent interaction parameter for PEG hydro-

gels in water: Application of a self learning algo-

rithm. Polymer, 2015. 1(66):p.135-147.

[28] Sabbagh, F., Muhamad, II., Nazari, Z., Mobini, P.,

Khatir, NM. Investigation of acyclovir-loaded,

acrylamide-based hydrogels for potential use as vag-

inal ring. Materials Today Communications, 2018.

1(16): p.274-280.

[29] Sirousazar, M., Kokabi, M., Hassan, ZM. In vivo

and cytotoxic assays of a poly (vinyl alcohol)/clay

nanocomposite hydrogel wound dressing. Journal of

Biomaterials Science, Polymer Edition. 2011.

22(8):p.1023-1033.

[30] Bostan, MS., Senol, M., Cig, T., Peker, I., Goren,

AC., Ozturk, T., Eroglu, MS. Controlled release of 5-

aminosalicylicacid from chitosan based pH and tem-

perature sensitive hydrogels. International journal of

biological macromolecules, 2013. 1(52):p. 177-183.

[31] Sabbagh, F., Muhamad, II., Nazari, Z., Mobini, P.,

Taraghdari, SB. From formulation of acrylamide-

based hydrogels to their optimization for drug release

using response surface methodology. Materials Sci-

ence and Engineering: C, 2018. 1(92): p. 20-25.

[32] Jensen, AT., Neto, WS., Ferreira, GR., Glenn, AF.,

Gambetta, R., Gonçalves, SB., Valadares, LF., Ma-

chado, F. Synthesis of polymer/inorganic hybrids

through heterophase polymerizations. InRecent De-

velopments in Polymer Macro, Micro and Nano

Blends, 2017. 1 (p. 207-235). Woodhead Publishing.

[33] van Keulen, H., Asseng, S. Simulation models as

tools for crop management. Encyclopedia of Sustain-

ability Science and Technology. 2018. p.1-20.

[34] García, MC., Uberman, PM. Nanohybrid Filler-

Based Drug-Delivery System. InNanocarriers for

Drug Delivery, 2019. 1 (p. 43-79). Elsevier.

[35] Popa, L., Ghica, MV., Dinu-Pîrvu, CE. Hydrogels-

Smart Materials for Biomedical Applications.

[36] Aguilar, MR., San, Román J. Introduction to smart

polymers and their applications. In Smart polymers

and their applications, 2019. 1 (p. 1-11). Woodhead

Publishing.

[37] Sabbagh, F., Muhamad, II. Production of poly-

hydroxyalkanoate as secondary metabolite with main

focus on sustainable energy. Renewable and Sustain-

able Energy Reviews, 2017. 1(72):p.95-104.

[38] Batista, AH., Rate, AW., Gilkes, RJ., Saunders, M.,

Dodd, A. Scanning and transmission analytical elec-

tron microscopy (STEM-EDX) can identify structur-

al forms of lead by mapping of clay crystals, Ge-

oderma 2018 15(310):p.191-200.

014. 2(99): p. 666-678.

[

15] Zhu, Y., Jiang, H., Ye, SH., Yoshizumi, T., Wagner,

WR. Tailoring the degradation rates of thermally re-

sponsive hydrogels designed for soft tissue injection

by varying the autocatalytic potential. Biomaterials,

015. 1(53): p.484-493.

16] Dragan, ES., Perju, MM., Dinu, MV. Preparation

and characterization of IPN composite hydrogels

based on polyacrylamide and chitosan and their in-

teraction with ionic dyes. Carbohydrate polymers,

012. 88(1): p.270-281.

17] Muhamad, II., Sabbagh, F., A Karim, NA. Polyhy-

droxyalkanoates: a valuable secondary metabolite

produced in microorganisms and plants. Plant Sec-

ondary Metabolites, Volume Three: Their Roles in

Stress Eco-Physiology, 2017. 6: p. 185.

18] Ohira, T., Yamamoto, O. Correlation between anti-

bacterial activity and crystallite size on ceramics.

Chemical engineering science, 2012. 68(1): p. 355-

[

61.

19] Kenne, L., Gohil, S., Nilsson, EM., Karlsson, A.,

Ericsson, D., Kenne, AH., Nord, LI. Modification

and cross-linking parameters in hyaluronic acid hy-

drogels—definitions and analytical methods. Carbo-

hydrate polymers, 2013. 91(1): p. 410-418.

[

20] Dash, R., Foston, M., Ragauskas, AJ. Improving the

mechanical and thermal properties of gelatin

hydrogels cross-linked by cellulose nanowhiskers.

Carbohydrate polymers, 2013. 91(2): p.638-645.

21] Rani, M., Agarwal, A., Maharana, T., Negi, YS. A

comparative study for interpenetrating polymeric

network (IPN) of chitosan-amino acid beads for

controlled drug release. African Journal of Pharmacy

and Pharmacology, 2010. 4(2): p.035-054.

[

22] Shalviri, A., Liu, Q., Abdekhodaie, MJ., Wu, XY.

Novel modified starch–xanthan gum hydrogels for

controlled drug delivery: Synthesis and characteriza-

tion. Carbohydrate Polymers, 2010. 79(4): p.898-

07.

23] Sabbagh, F., Muhamad, II. Acrylamide-based hy-

drogel drug delivery systems: release of acyclovir

from MgO nanocomposite hydrogel. Journal of the

Taiwan Institute of Chemical Engineers, 2017.

(72):p.182-193.

24] Santhanam, A., Sasidharan, S. Microbial production

of polyhydroxy alkanotes (PHA) from Alcaligens

spp. and Pseudomonas oleovorans using different

carbon sources. African Journal of Biotechnology,

[39] Sankaran, S., Becker, J., Wittmann, C., del Campo,

A. Optoregulated drug release from an engineered

living hydrogel.

[40] Puspitasari, T., Raja, KM., Pangerteni, DS., Patriati,

A., Putra, EG. Structural organization of poly (vinyl

alcohol) hydrogels obtained by freezing/thawing and

010.9(21):p.3144-3150.

[

25] Sabbagh, F., Muhamad, II. Physical and chemical

characterisation of acrylamide-based hydrogels,

Aam, Aam/NaCMC and Aam/NaCMC/MgO. Journal

γ-irradiation processes:

small-angle neutron

218