Synthesis and characterization of semi-interpenetrating polymer network hydrogel based on chitosan and poly(methacryloylglycylglycine)

ORIGINAL PAPER

Synthesis and characterization of semi-interpenetrating polymernetwork based on poly(dimethylsiloxane) and poly[2-(dimethylamino)ethyl methacrylate]

Fabio A. B. Silva • Fabio H. Florenzano •

Fabio L. Pissetti

Received: 1 December 2013 / Accepted: 27 February 2014 / Published online: 13 March 2014

� Springer Science+Business Media New York 2014

Abstract A semi-interpenetrating polymer network (semi-

IPN) based on poly(dimethylsiloxane) and poly[2-(dimethyl-

amino)ethyl methacrylate] (PDMAEMA) was prepared. The

material obtained was characterized by infrared spectrometry,

differential scanning calorimetry, thermogravimetric analysis

and scanning electronic microscopy. The results indicated the

presence of PDMAEMA into the semi-IPNs. Only the network

with the highest amount of crosslinker [(3-chloropropyl)tri-

methoxysilane] was stable in water. To evaluate the hydro-

philic/hydrophobic character of the obtained material, swelling

measurements were performed for the stable network in water

and in toluene. The semi-IPN was able to adsorb about 34 % in

mass of water, indicating that an appropriate hydrophylic/

hydrophobic balance was obtained. That behavior is desirable

since the material was designed for metal adsorption from

aqueous medium, without a lost in the ability to swell in less

polar solvents.

Keywords Poly(dimethylsiloxane) � Poly[2-

(dimethylamino)ethyl methacrylate] � Semi-

interpenetrating polymer network

1 Introduction

Poly(dimethylsiloxane) (PDMS), [–Si(CH3)2O–]n, which is

by far the most important polysiloxane and its derivative

materials may present many applications due to properties

such as: high flexibility, low surface tension, low chemical

reactivity, high thermal and oxidative stability, low curing

temperature, moldability, high hydrophobicity, good bio-

compatibility, among others [1–3].

Although PDMS materials present many advantages, its

hydrophobicity has limited their use in some applications [4, 5],

for instance, those involving adsorption of heavy metals from

aqueous effluents [6, 7]. Hydrophobicity can be lowered by the

preparation of semi-interpenetrated polymer networks (semi-

IPNs), which are blends between a polymer network and a

linear or branched polymer chain, held together by entangle-

ments between the two different polymer chains [8–13].

Various organic polymers may be used as the hydro-

philic component [14–16]. In this study, linear poly[2-

(dimethylamino)ethyl methacrylate] (PDMAEMA) was

chosen to generate a semi-IPN along with PDMS. This

polymer is derived from (2-dimethylamino)ethyl methac-

rylate, a monofunctional methacrylate monomer with a

polar tertiary amine group that offers water solubility and

potential to adsorb heavy metals [17–20].

In the current paper, semi-IPNs based on PDMS net-

work and linear PDMAEMA were prepared and charac-

terized using infrared spectrometry (FT-IR), differential

scanning calorimetry (DSC), thermogravimetric analysis

(TGA), scanning electron microscope (SEM) and swelling

measurements.

2 Experimental

2.1 Materials

(2-Dimethylamino)ethyl methacrylate (DMAEMA) (Sigma

Aldrich, 98 %), azobisisobutyronitrile (AIBN, Sigma

F. A. B. Silva � F. L. Pissetti (&)

Instituto de Quımica, Universidade Federal de Alfenas

(UNIFAL-MG), Alfenas, MG, Brazil

e-mail: [email protected]; [email protected]

F. H. Florenzano

Departamento de Engenharia de Materiais, Escola de Engenharia

de Lorena (EEL-USP), Universidade de Sao Paulo (USP),

Lorena, SP, Brazil

123

J Sol-Gel Sci Technol (2014) 72:227–232

DOI 10.1007/s10971-014-3320-x

Aldrich) were used to synthesize PDMAEMA. The inhibitor

added to the monomer was previously removed by using De-

Hibit-200 resin (Polysciences). Hydroxyl-terminated

poly(dimethylsiloxane) [PDMS(OH)2] (Sigma Aldrich, vis-

cosity 90–150 cSt), (3-chloropropyl)trimethoxysilane

(CPTMS) (Sigma Aldrich, 97 %), dibutyltin diacetate (Sigma

Aldrich) and tetrahydrofuran (THF) (Synth) were used in the

polysiloxane synthesis.

2.2 Preparation of PDMAEMA

The poly[2-(dimethylamino)ethyl methacrylate] was syn-

thesized by free radical polymerization (FRP) using DMA-

EMA monomer (32.3 mL or 0.191 mol), AIBN initiator

(24.6 mg) and toluene as solvent (40 mL) in a closed three-

neck flask connected to a condenser with a needle to flow

nitrogen when needed. The reaction solution was magneti-

cally stirred and oxygen was removed by bubbling nitrogen

gas. Polymerization was carried out at 70–90 �C for

approximately 2 h. The reaction mixture was immediately

cooled down to room temperature by immersion of the flask

in cold water. The obtained polymer was purified by cycles

of precipitation in hexane and solubilization with acetone,

being dried under vacuum at 45 �C for 48 h, obtaining a solid

material with a yield of 27.33 % (8.2 g).

2.3 Preparation of semi-IPNs

Semi-interpenetrating polymer networks were prepared

using a reaction mixture containing PDMS:PDMA-

EMA:CPTMS, with 1:0.5 weight ratio for PDMS:PDMA-

EMA. Two different materials having 1:0.4 and 1:1 molar

ratios of PDMS:CPTMS were obtained and named as

PPCl1 and PPCl2, respectively. The catalyst used was

dibutyltin diacetate 1 % by weight relative to PDMS.

Tetrahydrofuran (THF) (PDMS:THF 1:1 w:v) was used as

solvent. The mixture was stirred for 30 min. The resulting

viscous solution was poured in TeflonTM petri dishes and

left at room temperature obtaining the materials as solid

films. Semi-IPNs were then kept in water for 15 days,

powdered and washed again with tetrahydrofuran. Finally

the materials were dried under vacuum at 45 �C for 48 h.

The semi-IPNs were immersed in water for 15 days to

remove the PDMAEMA chains that were not retained into

the PDMS network. After powdered, the materials were

washed again with THF to remove the fraction of not

entangled PDMAEMA, unreacted reagents, and conden-

sation byproducts of the PDMS networks.

2.4 Infrared spectrometry (FT-IR)

The FT-IR spectra were obtained in KBr pellets using a

Shimadzu Prestige spectrophotometer. A spectral resolution

of 2 cm-1 was employed and 20 scans were acquired for

each spectrum over the range of 4,000–400 cm-1.

2.5 Differential scanning calorimetry (DSC)

Differential scanning calorimetry was carried out on a

Seiko Exstar 7020 under flowing nitrogen (50 mL min-1),

with temperature range of 10 �C up to 80 �C at a heating

rate of 3 �C min-1.

2.6 Thermogravimetric analysis (TGA)

Thermogravimetric analyses of the samples were recorded

on a Seiko Exstar 7300, under nitrogen (50 mL min-1) at a

heating rate of 20 �C min-1 over a temperature range from

30 to 900 �C.

2.7 Scanning electron microscope (SEM)

Scanning electron microscope experiments were performed

on a Zeiss LEO 1450 VP scanning electron microscope

with an accelerating voltage of 20 kV. Sample films were

dried at 60 �C for 1 day before the experiment. The sam-

ples were previously covered with a thin Au layer using a

BALTEC MED 020 sputtering instrument.

2.8 Swelling measurements

The swelling measurements for PPCl2 films were obtained

at room temperature. The samples were cut (1 9 2 cm) and

dried. After that, the samples were weighed (0.3837 and

0.3933 g) and immersed either in water or in toluene,

respectively. The mass of the swollen film in each solvent

were recorded at different times. The swelling ratio was

calculated by the ratio between the mass of the film swollen

and dried.

3 Results and discussion

The obtained semi-IPN can be described as a polymeric

network in which the nodes consist of silsesquioxane

clusters generated from the condensation of PDMS with

alkoxysilane [2, 21], in which the PDMAEMA were

entangled in the linear PDMS chains. These siloxane bonds

were formed by condensation of PDMS(OH)2 with silanol

or alkoxy functions of the crosslinker (CPTMS). Schematic

illustrations of the obtained semi-IPNs are shown in Fig. 1.

3.1 Infrared spectrometry

The FT-IR spectra of the PDMAEMA, PPCl1 and PPCl2

are shown in Fig. 2. For the semi-IPNs, two bands can be

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observed in the 1,100–1,020 cm-1 region, due to the

asymmetric stretching of the PDMS siloxane bond. The

asymmetrical and symmetrical deformations of CH3 bond

of PDMS appears at 1,414 and 1,261 cm-1, respectively.

The absorptions at 867 and 803 cm-1 can be related to the

rocking deformation of C–H and Si–C, respectively [6].

The bands at 1,637 and 1,729 cm-1 were assigned to

C=O and –COO– stretching vibration, respectively, indi-

cating the presence of PDMAEMA in the prepared semi-

IPNs [22, 23].

3.2 Differential scanning calorimetry (DSC)

Figure 3 presents the DSC curve for PDMAEMA, PPCl1 and

PPCl2. On the curve b was possible to identify the Tg of the

PDMAEMA into the PPCl2, at 29 oC [24, 25]. The

PDMAEMA Tg was not observed for PPCl1, suggesting that

the remaining amount of organic polymer for that semi-IPN

was low (as also suggested by FT-IR spectra). The results

indicate that semi-IPN based on PDMS and PDMAEMA was

obtained only with higher amount of crosslinker (PPCl2).

3.3 Thermogravimetric analysis (TGA)

Figure 4 presents the thermogravimetric (TGA) and dif-

ferential thermogravimetry (DTG) curves of the PDMA-

EMA, PPCl2 and PPCl1. The organic polymer showed no

significant weight change up to 245 �C. A weight loss of

about 50 % starting at 365 �C was observed, followed by

another event at 580 �C until complete decomposition [23,

Fig. 1 Idealized structure of the

PDMAEMA/PDMS semi-IPN

Fig. 2 FT-IR spectra of a PDMAEMA, b PPCl2 and c PPCl1

Fig. 3 DSC curves of a PDMAEMA, b PPCl2 and c PPCl1

J Sol-Gel Sci Technol (2014) 72:227–232 229

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26]. For PPCl2, an initial weight loss of 9 % occurred until

160 �C, which can be associated with the physical

desorption of water moisture. Weight losses of 13 % up to

260 �C and 15 % up to 350 �C, suggests the degradation of

PDMAEMA. The 18 % of weight loss up to 455 �C and

33 % up to 900 �C can be ascribed to degradation of

CPTMS as observed in previous works [6, 7, 21]. The

residue of 12 % indicated a high amount of reticulation,

since the PDAMEMA catalyzes the PDMS degradation.

For PPCl1, also occurred an initial weight loss related with

the physical desorption of water moisture, followed by a

weight loss which can be associated with degradation of

PDMAEMA and depolymerization of the PDMS chains

with a 28 % of residue [27]. As observed in the region from

(a)

(b)

(c)

Fig. 4 TGA and DTG curves of a PDMAEMA, b PPCl2 and c PPCl1

Fig. 5 SEM micrographs of the PPCl2 semi-IPN surface at different

magnifications

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123

260 to 350 �C, this result also suggests that the low amount

of PDMAEMA remain in the semi-IPN PPCl1.

3.4 Scanning electron microscope (SEM)

Figure 5 shows the micrographs of PPCl2 semi-IPN at dif-

ferent magnifications. The material exhibited a homogenous

morphology with a wavelike pattern. Pure PDMS films

present a dense and smooth surface and a non-porous mor-

phology [28, 29]. At the Fig. 5b, c can be observed a grain with

different morphology, indicating the formation of sils-

esquioxane clusters which reach the surface of the PDMS

network [30]. The SEM results indicated that the PDMAEMA

chains were entangled in the PDMS network with a high

dispersion and kept the main characteristics of the PDMS.

3.5 Swelling measurements

The swelling ratio versus time for PPCl2 film in water and

toluene are shown in Fig. 6.

The semi-IPN showed higher swelling ratio in contact

with toluene reaching the steady point with a swelling ratio

of 2.14, after approximately 15 h [7, 8].

For water, the swelling ratio was 1.34, after 13 days. A

suggested explanation for the behavior is that the hydrophilic

PDMAEMA chains are deeper inside the polymeric networks

that on the surface of the Semi-IPN, leading to a slower

swelling. Another factor might be the hydrophobic character

of the PDMS network surface, hindering water diffusion into

the film [13]. Based on the swelling behavior, the semi-IPN

(PPCL2) seems to have amphiphilic character and has

potential to be used in studies performed in aqueous solutions

as well as in other liquid ambient for metal adsorption.

4 Conclusions

The work describes a synthetic route to obtain an semi-

interpenetrating polymer network based on poly(dimeth-

ylsiloxane) and poly[2-(dimethylamino)ethyl methacry-

late]. The data obtained with FT-IR, TGA, DSC and SEM

indicates that PDMAEMA was entangled efficiently only

in the network prepared with the highest amount of

crosslinker (PPCl2). It has been observed on swelling

measurements an adsorption of 34 % (in mass) of water,

indicating that the semi-IPN obtained presents an higher

hydrophilic character when compared with PDMS. The

crosslinking agent for preparation of semi-IPNs or IPNs

with PDMS, described in the literature, generally is tetra-

ethyl orthosilicate (TEOS). In this work we are able to

obtain a PDMS network which interact with water effi-

ciently using other crosslinking agent (CTPMS), without

losing the well know affinity of the PDMS with apolar

solvents. The authors intend to study the material potential

for metal adsorption in aqueous and no-aqueous systems.

Acknowledgments The authors are indebted to CAPES for the F.

A. B. S. fellowship, FAPESP, CNPq and FAPEMIG for their financial

support. The authors thank Dr. Durval Rodrigues Jr. from EEL-USP

for kindly providing the SEM instrumentation.

References

1. Mark JE (2004) Some interesting things about polysiloxanes. Acc

Chem Res 12:946–953

2. Zhang X, Lin G, Kumar SR, Mark JE (2009) Hydrogels prepared

from polysiloxane chains by end linking them with trifunctional

silanes containing hydrophilic groups. Polymer 23:5414–5421

3. McCarthy PW, Zheng TJ (2010) Rediscovering silicones:

molecularly smooth, low surface energy, unfilled, UV/Vis-

transparent, extremely cross-linked, thermally stable, hard, elastic

PDMS. Langmuir 24:18585–18590

4. Eddington DT, Puccinelli JP, Beebe DJ (2006) Thermal aging

and reduced hydrophobic recovery of polydimethylsiloxane. Sens

Actuators B Chem 1:170–172

5. Zhou JW, Ellis AV, Voelcker NH (2010) Recent developments in

PDMS surface modification for microfluidic devices. Electro-

phoresis 1:2–16

6. Pissetti FL, Yoshida IVR, Gushikem Y, Kholin YV (2008) Metal

ions adsorption from ethanol solutions on ethylenediamine-modi

fled poly(dimethylsiloxane) elastomeric network. Colloids Surf

Physicochem Eng Aspects 1–3:21–27

7. Pissetti FL, Magosso HA, Yoshida IVP, Gushikem Y, Myernyi

SO, Kholin YV (2007) n-Propylpyridinium chloride-modified

poly (dimethylsiloxane) elastomeric networks: preparation,

characterization, and study of metal chloride adsorption from

ethanol solutions. J Colloid Interface Sci 1:38–45

8. Marques RS, Mac Leod TCO, Yoshida IVP, Mano V, Assis MD,

Schiavon MA (2010) Synthesis and characterization of semi-

interpenetrating networks based on poly(dimethylsiloxane) and

poly(vinyl alcohol). J Appl Polym Sci 1:158–166

9. Erbil C, Kazancıoglu E, Uyanık N (2004) Synthesis, character-

ization and thermoreversible behaviours of poly(dimethyl

Fig. 6 Swelling ratio versus time of the PPCl2 in (filled triangles)

toluene and (open circles) water

J Sol-Gel Sci Technol (2014) 72:227–232 231

123

siloxane)/poly(N-isopropyl acrylamide) semi-interpenetrating

networks. Eur Polym J 6:1145–1154

10. Rodkate N, Wichai U, Boontha B, Rutnakornpituk M (2010)

Semi-interpenetrating polymer network hydrogels between

polydimethylsiloxane/polyethylene glycol and chitosan. Carbo-

hydr Polym 3:617–625

11. Kohane TR, Hoare DS (2008) Hydrogels in drug delivery: pro-

gress and challenges. Polymer 8:1993–2007

12. Mespouille L, Hedrick JL, Dubois P (2009) Expanding the role of

chemistry to produce new amphiphilic polymer (co)networks.

Soft Matter 24:4878

13. Panou AI, Papadokostaki KG, Tarantili PA, Sanopoulou M

(2013) Effect of hydrophilic inclusions on PDMS crosslinking

reaction and its interrelation with mechanical and water sorption

properties of cured films. Eur Polym J 7:1803–1810

14. Zhang N, Shen Y, Li X, Cai S, Liu M (2012) Synthesis and

characterization of thermo- and pH-sensitive poly(vinyl alcohol)/

poly(N, N-diethylacrylamide-co-itaconic acid) semi-IPN hydro-

gels. Biomed Mater 3:035014

15. Garg P, Singh RP, Choudhary V (2011) Selective poly-

dimethylsiloxane/polyimide blended IPN pervaporation mem-

brane for methanol/toluene azeotrope separation. Sep Purif

Technol 3:407–418

16. Castellino V, Acosta E, Cheng Y-L (2012) Interpenetrating

polymer networks templated on bicontinuous microemulsions

containing silicone oil, methacrylic acid, and hydroxyethyl

methacrylate. Colloid Polym Sci 3:527–539

17. Gao B, Chen Y, Zhang Z (2010) Preparation of functional

composite grafted particles PDMAEMA/SiO2 and preliminarily

study on functionality. Appl Surf Sci 1:254–260

18. Tokuyama H, Ishihara N (2010) Temperature-swing adsorption

of precious metal ions onto poly(2-(dimethylamino)ethyl meth-

acrylate) gel. React Funct Polym 9:610–615

19. Kavakh PA, Yilmaz Z, Sen M (2007) Investigation of heavy

metal ion adsorption characteristics of poly(N, N dimethylamino

ethylmethacrylate) hydrogels. Sep Sci Technol 6:1245–1254

20. Qiu J, Wang Z, Li H, Xu L, Peng J, Zhai M, Yang C, Li J, Wei G

(2009) Adsorption of Cr(VI) using silica-based adsorbent pre-

pared by radiation-induced grafting. J Hazard Mater 1:270–276

21. Pissetti FAB, Silva FL (2014) Adsorption of cadmium ions on

thiol or sulfonic-functionalized poly(dimethylsiloxane) networks.

J Colloid Interface Sci 15:95–100

22. Estrada-Villegas GM, Macossay J, Bucio E (2010) c-Ray-

induced grafting of DMAEMA and AAc onto PP by two step

method. J Radioanal Nucl Chem 1:131–135

23. Bucio AR, Hernandez-Martınez E (2009) Radiation-induced

grafting of stimuli-responsive binary monomers: PDMAEMA/

PEGMEMA onto PP films. J Radioanal Nucl Chem 3:559–563

24. Gao C, Liu M, Chen J, Chen C (2012) Physicochemical char-

acterization and drug release properties of PDMAEMA/OSA

semi-IPN hydrogels with microporous structure. Polym Adv

Technol 3:389–397

25. Chen SC, Kuo SW, Liao CS, Chang FC (2008) Syntheses, spe-

cific interactions, and pH-sensitive micellization behavior of poly

vinylphenol-b-2-(dimethylamino)ethyl methacrylate diblock

copolymers. Macromolecules 22:8865–8876

26. Pal S, Ghosh Roy S, De P (2014) Synthesis via RAFT poly-

merization of thermo- and pH-responsive random copolymers

containing cholic acid moieties and their self-assembly in water.

Polym Chem 5:1275–1284

27. Zheng Y, Tan Y, Dai L, Lv Z, Zhang X, Xie Z, Zhang Z (2012)

Synthesis, characterization, and thermal properties of new poly-

siloxanes containing 1,3-bis(silyl)-2,4-dimethyl-2,4-diphenylcy-

clodisilazane. Polym Degrad Stabil 11:2449–2459

28. Li S, Qin F, Qin P, Karim MN, Tan T (2013) Preparation of

PDMS membrane using water as solvent for pervaporation sep-

aration of butanol–water mixture. Green Chem 8:2180–2190

29. Naeimi M, Karkhaneh A, Barzin J, Khorasani MT, Ghaffarieh A

(2013) Novel PDMS-based membranes: sodium chloride and

glucose permeability. J Appl Polym Sci 5:3940–3947

30. Chen DZ, Liu Y, Huang C (2012) Synergistic effect between

POSS and fumed silica on thermal stabilities and mechanical

properties of room temperature vulcanized (RTV) silicone rub-

bers. Polym Degrad Stabil 3:308–315

232 J Sol-Gel Sci Technol (2014) 72:227–232

123