**3.2. Polymeric coatings deposited on PP nonwovens**

Nonwovens constitute a specific substrate for depositing thin polymeric layers. The nonwoven surface is developed to an extent dependent on the diameter of elementary fibers, density of their distribution and the formation technique used. The melt-blown PP nonwovens (see section 3.1.2.) were coated with thin layers of plasma polymers in a methane plasma and in hexamethyldisiloxane (HMDSO: O-(Si-(CH3)2) vapors [Urbaniak-Domagala et al, 2010). As a result of this process, the nonwoven surface was covered with a plasma polymer layer with a thickness of about 100 nm. SEM photographs (Figure 7) indicate that the coating obtained shows a character of a continuous film fitted to the uneven nonwoven surface covering only the elementary fibers in the near-surface nonwoven layer.

Sample A Sample B

**Figure 7.** SEM images of PP fibers at nonwoven fabrics, treated methane plasma (Sample A), treated HMDSO plasma ( Sample B). Plasma process time 10 min., pressure 0.05Tr, power 100W.

The FTIR-ATR spectrogram of the methane plasma-modified nonwoven surface (Figure 8) indicates that the layer chemical structure has a character of a hydrocarbon polymer as the PP substrate. The broad band with a maximal absorption at 1650 cm-1 can be assumed as a post-treatment effect (Guruvenket et al, 2004).

The IR-ATR spectrogram of the HMDSO plasma-modified nonwoven indicates that the layer deposited has a chemical structure of a SiOC:H polymer (Creatore et al., 2002) and contains intensive absorption bands at 800 cm-1, 841 cm-1, 1040 cm-1and 1256cm-1 (Table 2) being characteristic of chemical groups containing silicon (Borvon et al., 2002).

but also its functionalization.

nonwoven layer.

**3.2. Polymeric coatings deposited on PP nonwovens** 

group – OH (Kazicina.&Kupletska, 1976). One may assume that the air plasma oxidizes the fiber surface with the aid of reactive oxygen, peroxide and nitrogen groups that together with electrons react with the PP fiber surface causing not only the etching of surface layer

Nonwovens constitute a specific substrate for depositing thin polymeric layers. The nonwoven surface is developed to an extent dependent on the diameter of elementary fibers, density of their distribution and the formation technique used. The melt-blown PP nonwovens (see section 3.1.2.) were coated with thin layers of plasma polymers in a methane plasma and in hexamethyldisiloxane (HMDSO: O-(Si-(CH3)2) vapors [Urbaniak-Domagala et al, 2010). As a result of this process, the nonwoven surface was covered with a plasma polymer layer with a thickness of about 100 nm. SEM photographs (Figure 7) indicate that the coating obtained shows a character of a continuous film fitted to the uneven nonwoven surface covering only the elementary fibers in the near-surface

**Figure 7.** SEM images of PP fibers at nonwoven fabrics, treated methane plasma (Sample A), treated

The FTIR-ATR spectrogram of the methane plasma-modified nonwoven surface (Figure 8) indicates that the layer chemical structure has a character of a hydrocarbon polymer as the PP substrate. The broad band with a maximal absorption at 1650 cm-1 can be assumed as a

The IR-ATR spectrogram of the HMDSO plasma-modified nonwoven indicates that the layer deposited has a chemical structure of a SiOC:H polymer (Creatore et al., 2002) and contains intensive absorption bands at 800 cm-1, 841 cm-1, 1040 cm-1and 1256cm-1 (Table 2)

Sample A Sample B

post-treatment effect (Guruvenket et al, 2004).

HMDSO plasma ( Sample B). Plasma process time 10 min., pressure 0.05Tr, power 100W.

being characteristic of chemical groups containing silicon (Borvon et al., 2002).

**Figure 8.** FTIR-ATR spectra of PP nonwoves. Sample 1- untreated, Sample 2 - methane plasma treated: power 25W, pressure 0.05Tr, Sample 3 - methane plasma treated: power 100W, pressure 0.05Tr.

**Figure 9.** FTIR-ATR spectra of PP nonwoves. Sample 1 - untreated, Sample 2 - HMDSO plasma treated: power 25W, pressure 0.1Tr, Sample 3 - HMDSO plasma treated: power 100W, pressure 0.1Tr.

The assessment of the surface of samples was carried out in the diamond-sample system, in which the IR radiation beam penetrates the layer 2 μm in depth within the spectrum range discussed. The penetration depth of the IR radiation beam considerably exceeds the thickness of the p-HMDSO layer (~ 0.1 m), hence characteristic bands of PP substrate also occur in the absorption spectrum.


\*) s - stretching vibration symmetrical and a -asymmetrical, - deformation vibration, r – rocking vibration

**Table 2.** IR absorption bands of p-HMDSO plasma layers (Aumaille et al., 2002; Agres et al., 1996)

## **3.3. Testing polymeric coatings containing polypyrroles**

Polypyrrole is a polymer widely used in commodity production owing to its high thermal stability, resistance to atmospheric conditions and biocompatibility. Its important advantages include electric properties. Using appropriate synthesis conditions, one can obtain electro-conductive, semi-conductive or electro-insulating polypyrroles. In view of processing difficulties, polypyrroles are produced directly on material surfaces in the form of coatings by "*in situ"* chemical, electrochemical or plasma methods. Moreover, polypyrroles are used to make composites as reinforcing and functional materials. In this work, the FTIR-ATR technique was used to monitor the results of polypyrrole synthesis by chemical and plasma methods and the preparation of pyrrole - containing composites.

## *3.3.1. Formation of latex-pyrrole composites*

Polypyrrole (PPy) was used to make an electro-conductive composite as a backing of textile floor coverings (TFC). The TFC piles are fixed in a standard procedure with the use of dressing containing a synthetic rubber and vinyl-acrylic thickeners. The standard latex coating shows electro-insulating properties and impedes the leakage of static charges generated on the TFC pile during exploitation. A functional dressing was prepared to facilitate the leakage of static charges from TFC. PPy microspheres in the form of an aqueous dispersion, prepared by polymerization in an aqueous solution of ferric chloride, were added to an aqueous dispersion of butadiene-styrene-carboxyl copolymer (LBSK 4148) (Urbaniak-Domagala, 2005).

The dispersion components were intermixed by means of an ultrasonic stirrer and the resultant dressing was applied on the bottom of a raw TFC followed by the cross-linking process. The volume resistance tests of the latex-PPy coat confirmed its antistatic properties already with a 3% (by wt.) content of PPy in relation to the dry copolymer mass in the dressing.

occur in the absorption spectrum.

The assessment of the surface of samples was carried out in the diamond-sample system, in which the IR radiation beam penetrates the layer 2 μm in depth within the spectrum range discussed. The penetration depth of the IR radiation beam considerably exceeds the thickness of the p-HMDSO layer (~ 0.1 m), hence characteristic bands of PP substrate also

Wave number, cm-1 Absorbing group and type of vibration 1410 s (CH3), a in Si(CH3)x 1256 CHx, (CH3)in Si(CH3)x

840 Si(CH3)x , r (CH3)in Si(CH3)3 800 (Si-O-Si), r (CH3)in Si(CH3)2 \*) s - stretching vibration symmetrical and a -asymmetrical, - deformation vibration, r – rocking vibration **Table 2.** IR absorption bands of p-HMDSO plasma layers (Aumaille et al., 2002; Agres et al., 1996)

Polypyrrole is a polymer widely used in commodity production owing to its high thermal stability, resistance to atmospheric conditions and biocompatibility. Its important advantages include electric properties. Using appropriate synthesis conditions, one can obtain electro-conductive, semi-conductive or electro-insulating polypyrroles. In view of processing difficulties, polypyrroles are produced directly on material surfaces in the form of coatings by "*in situ"* chemical, electrochemical or plasma methods. Moreover, polypyrroles are used to make composites as reinforcing and functional materials. In this work, the FTIR-ATR technique was used to monitor the results of polypyrrole synthesis by chemical and plasma methods and the preparation of pyrrole - containing composites.

Polypyrrole (PPy) was used to make an electro-conductive composite as a backing of textile floor coverings (TFC). The TFC piles are fixed in a standard procedure with the use of dressing containing a synthetic rubber and vinyl-acrylic thickeners. The standard latex coating shows electro-insulating properties and impedes the leakage of static charges generated on the TFC pile during exploitation. A functional dressing was prepared to facilitate the leakage of static charges from TFC. PPy microspheres in the form of an aqueous dispersion, prepared by polymerization in an aqueous solution of ferric chloride, were added to an aqueous dispersion of butadiene-styrene-carboxyl copolymer (LBSK 4148)

The dispersion components were intermixed by means of an ultrasonic stirrer and the resultant dressing was applied on the bottom of a raw TFC followed by the cross-linking process. The volume resistance tests of the latex-PPy coat confirmed its antistatic properties already with a

3% (by wt.) content of PPy in relation to the dry copolymer mass in the dressing.

1040 a (Si-O-Si)

**3.3. Testing polymeric coatings containing polypyrroles** 

*3.3.1. Formation of latex-pyrrole composites* 

(Urbaniak-Domagala, 2005).

**Figure 10.** FTIR-ATR spectra pure latex LBSK 4148 (Sample 1), chemically synthesized polypyrrole (Sample 2), latex/PPy composite containing 2 wt% PPy (Sample 3), 3 wt% PPy (Sample 4)

The percolation of the coating electric conduction has a continuous character and the percolation threshold is relatively low. The coating formation on the TFC bottom was controlled by means of FTIR-ATR spectrometry

Changes in the IR radiation absorbance of the coatings were observed within the range from 600 cm-1 to 1700 cm-1. Figure 10 shows the absorption spectra of pure LBSK 4148 latex (Sample 1), pure PPy (Sample 2) and two samples of LBSK-PPy composite containing 2% by wt. of PPy and 3% by wt. of PPy, respectively. The locations of absorption bands of LBSK, PPy and LBSK-PPy composite containing 3% by wt. of PPy are listed in Table 3.

The spectrum of LBSK indicates the presence of three types of butadiene isomeric units (1,4 cis, 1,4-trans and 1,2-vinyl), styrene PS and carboxyl (Molenda et al.,1998; Munteanu & Vasile, 2005) have carried out fundamental research of FT-IR spectra of butadiene-styrene copolymers with various structural arrangements (block and linear copolymers, block copolymers of the star type and statistic copolymers). The type of spectrum found for LBSK 4148 latex indicates the architecture of statistic copolymer. The spectrogram of the microspheres of chemically synthesized PPy (powder) indicates PPy rings in the polymer structure and groups connected with the ring being consistent with the results of authors (Eisazadeh, 2007; Cruz 1999; Ji-Ye Jin et al.,1991).


**Table 3.** The FTIR absorption bands for latex LBSK 4148, chemically synthesized polypyrrole and LBSK 4148/PPy composite containing 3 wag.% PPy (Kazicina.&Kupletska, 1976, Molenda et al.,1998; Munteanu & Vasile, 2005; Bieliński et al., 2009; Eisazadeh, 2007; Cruz 1999; Ji-Ye Jin et al.,1991)

The spectrograms of LBSK-PPy composite samples indicate the superposition of characteristic bands of the composite components: PPy and latex. As the PPy content in the composite increases, one can observe an increase in the intensity of characteristic peaks of PPy, but the quantitative analysis of the composite is difficult to perform due to great differences in the absorbance of the composite components (latex is white, PPy is black). The band maxima shown by the PPy powder are delocalized in the spectrum of latex-PPy composite. The band indicating the pyrrole ring vibration at 1530cm-1 is shifted towards a higher frequency to 1548 cm-1. The bands of groups linked up to the pyrrole ring are also shifted: for CH deformation vibration (out of plane quinol PPy) from 1026 cm-1 to 1040 cm-1, for C-N deformation vibration from 1143 cm-1 to 1170 cm-1, and for the valence vibration of CN in pyrrole ring from 1284 cm-1 to 1300 cm-1. The shifts of bands can be due to the scattering of IR radiation in the structure of PPy powder, but they can also indicate the occurrence of PPy - latex intermolecular interactions, with which the oscillatory excitation of chemical groups in PPy requires a higher energy.

#### *3.3.2. Synthesis of polypyrroles*

98 Advanced Aspects of Spectroscopy

cm-1 Absorbing group and type of vibration ,

(CH) out of plane in the aromatic ring,




<sup>1638</sup> (C=C) PS units

<sup>911</sup> (CH) out of plane near the double bond

<sup>966</sup> (CH) out of plane near the double bond

,

699, 758

LBSK 4148 Chemically synthesized polypyrrole

cm-1



1451 (CH) in cis-PB, trans-PB, vinyl-PB units - 1451 1492 (C=C) in aromatic ring PS units - -

1600 (C=C) in aromatic ring PS units - -

1700 (C=O) - 1700 **Table 3.** The FTIR absorption bands for latex LBSK 4148, chemically synthesized polypyrrole and LBSK

The spectrograms of LBSK-PPy composite samples indicate the superposition of characteristic bands of the composite components: PPy and latex. As the PPy content in the composite increases, one can observe an increase in the intensity of characteristic peaks of PPy, but the quantitative analysis of the composite is difficult to perform due to great differences in the absorbance of the composite components (latex is white, PPy is black). The band maxima shown by the PPy powder are delocalized in the spectrum of latex-PPy composite. The band indicating the pyrrole ring vibration at 1530cm-1 is shifted towards a higher frequency to 1548 cm-1. The bands of groups linked up to the pyrrole ring are also shifted: for CH deformation vibration (out of plane quinol PPy) from 1026 cm-1 to 1040 cm-1, for C-N deformation vibration from 1143 cm-1 to 1170 cm-1, and for the valence vibration of CN in pyrrole ring from 1284 cm-1 to 1300 cm-1. The shifts of bands can be due to the scattering of IR radiation in the structure of PPy powder, but they can also indicate the occurrence of PPy - latex intermolecular

4148/PPy composite containing 3 wag.% PPy (Kazicina.&Kupletska, 1976, Molenda et al.,1998; Munteanu & Vasile, 2005; Bieliński et al., 2009; Eisazadeh, 2007; Cruz 1999; Ji-Ye Jin et al.,1991)

(C=C) in vinyl-PB - -


(PPy)

PS units - 699, 758

of the vinyl-PB units - 911

in trans-PB units - 966

Absorbing group and type of

 (C-H) out of plane pyrrole ring, (NH2), (C-N-C), (C-N-C)

 (N-H), (C-H), pyrrole rings pulsation (C-N) secondary amines

(C=C) in pyrrole ring (C=N) in pyrrole ring , pyrrole ring pulsation

(C-N) in pyrrole ring <sup>1300</sup>

vibration , cm-1

LBSK 4148/PPy

790

1040

1548

Below are presented examples of using the FTIR-ATR technique to assess the progress in the synthesis of PPy. The polymerization of pyrrole was carried out by chemical and plasma methods. Thin layers of PPy were formed on the surface of a PP film by the *in situ*  technique.

#### *3.3.2.1. Chemical polymerization method*

Polymer layers were formed by the polymerization of pyrrole according to the redox mechanism. Two media of pyrrole oxidation were used: an aqueous solution of ferric chloride and aqueous solution of ammonium sulfate with p-toluenesulfonic acid as dopant. Based on the FTIR-ATR spectrum of the polymer, its synthesis progress and chemical structure were characterized. Figure 11 shows examples of the spectra of PPy synthesized in both media for 2h and 5 h.

**Figure 11.** FTIR-ATR spectra chemically synthesized polypyrrole. Sample 1 - PPy powder (molar ratio of FeCl3:Py=2,3:1) - polymerization time 5h; PPy layers on the polypropylene foil: Sample 2 – molar ratio of FeCl3:Py=2,3:1, polymerization time 5h, Sample 3 – molar ratio of FeCl3:Py=2,3:1, polymerization time 2h; Sample 4 – molar ratio of (NH4)2S2O8: CH3C6H4SO3H: Py=0,2:0,25:1, polymerization time 2h.

The spectra of PPy are recorded on the PP substrate. Owing to the low thickness of layers (0.1 - 1m), the spectrum additionally contains bands derived from the substrate. For comparison, the spectral characteristics of PPy synthesized in the form of powder were also presented. The absorption spectra of all the polymer samples within the wave number range of 600 cm-1 – 1800 cm-1 confirm the presence of pyrrole group (Table 3). The intensity of absorption bands increases with increasing polymerization time, which is due to the increased layer thickness. In the process of chemical synthesis, the aromatic character of pyrrole ring is maintained, which results in the formation of conjugated double bonds in the linear macromolecule chain. In the presence of admixtures intercalated to the system, the polymer is electro-conductive (incorporated dopants: Cl and CH3C6H4SO3- ). The oxidized form of conductive PPy obtained shows a considerable absorption of IR radiation (black color of the polymer). The spectrogram of PPy synthesized with the use of two different oxidants shows no differences between the polymer chemical structures. Differences concern the progress rate of the synthesis: the higher intensity of pyrrole group bands in the polymer synthesized in the aqueous solution of ferric chloride indicates a higher polymerization rate, which is confirmed by the higher rate of layer building up.

#### *3.3.2.2. Plasma polymerization method*

Polymer synthesis performed in glow discharge of monomer vapors is a dry, ecological, energy- and material-saving process. The polymerization process is initiated by means of electrons and radicals formed in the gas discharge. The polymerization of pyrrole was carried out in a flow reactor, in glow discharge of the induction type by means of RF field 13.56 MHz (Urbaniak-Domagala, 2008). PP film substrate was centrally and axially placed on a glass carrier in the reactor. The film surface was preliminary purified by means of argon plasma followed by the deposition of the plasma polymer. The FTIR-ATR technique was used to examine the effect of process parameters, such as deposition time, pressure in the reactor and power input to the reactor, on the chemical structure of plasma polymer. In order to impart semi-conductive properties, the plasma PPy was doped after the deposition process by two methods: *in situ* in the reactor in glow discharge of the vapors of organic iodine compounds, and *ex situ* after removal from the reactor in crystalline iodine vapors.

Figure 12 shows the FTIR spectra of the plasma polymer within the range of (600-1850) cm-1. The spectrogram shows the superposition of the absorption bands of plasma polymer (thickness 0.3 m) and PP substrate. The broad band at (1500 – 1800) cm-1 indicates different structure of plasma PPy compared to that of PPy synthesized by the chemical method. This band points to a possible occurrence of primary and secondary amines , secondary amides (Kazicina.&Kupletska, 1976), and carbonyl groups (Ji-Ye Jin et al.,1991) in the polymer. The broad absorption band of the polymer indicates a complex absorption caused by the products of broken pyrrole rings that initiate the branching and cross-linking of the polymer followed by various substitutions. Thus the plasma spectrograms can show secondary and tertiary amines that complicate the absorption in this range. Moreover, one cannot exclude the occurrence of the band at 1710cm-1 that, according to authors (Ji-Ye Jin et al.,1991) indicates the presence of carbonyl groups. This band is often observed in neutral or weakly doped forms of PPy, mainly due to their susceptibility to oxidation in air. The spectrum of

The spectra of PPy are recorded on the PP substrate. Owing to the low thickness of layers (0.1 - 1m), the spectrum additionally contains bands derived from the substrate. For comparison, the spectral characteristics of PPy synthesized in the form of powder were also presented. The absorption spectra of all the polymer samples within the wave number range of 600 cm-1 – 1800 cm-1 confirm the presence of pyrrole group (Table 3). The intensity of absorption bands increases with increasing polymerization time, which is due to the increased layer thickness. In the process of chemical synthesis, the aromatic character of pyrrole ring is maintained, which results in the formation of conjugated double bonds in the linear macromolecule chain. In the presence of admixtures intercalated to the system, the

form of conductive PPy obtained shows a considerable absorption of IR radiation (black color of the polymer). The spectrogram of PPy synthesized with the use of two different oxidants shows no differences between the polymer chemical structures. Differences concern the progress rate of the synthesis: the higher intensity of pyrrole group bands in the polymer synthesized in the aqueous solution of ferric chloride indicates a higher

Polymer synthesis performed in glow discharge of monomer vapors is a dry, ecological, energy- and material-saving process. The polymerization process is initiated by means of electrons and radicals formed in the gas discharge. The polymerization of pyrrole was carried out in a flow reactor, in glow discharge of the induction type by means of RF field 13.56 MHz (Urbaniak-Domagala, 2008). PP film substrate was centrally and axially placed on a glass carrier in the reactor. The film surface was preliminary purified by means of argon plasma followed by the deposition of the plasma polymer. The FTIR-ATR technique was used to examine the effect of process parameters, such as deposition time, pressure in the reactor and power input to the reactor, on the chemical structure of plasma polymer. In order to impart semi-conductive properties, the plasma PPy was doped after the deposition process by two methods: *in situ* in the reactor in glow discharge of the vapors of organic iodine compounds, and *ex situ* after removal from the reactor in crystalline iodine vapors.

Figure 12 shows the FTIR spectra of the plasma polymer within the range of (600-1850) cm-1. The spectrogram shows the superposition of the absorption bands of plasma polymer (thickness 0.3 m) and PP substrate. The broad band at (1500 – 1800) cm-1 indicates different structure of plasma PPy compared to that of PPy synthesized by the chemical method. This band points to a possible occurrence of primary and secondary amines , secondary amides (Kazicina.&Kupletska, 1976), and carbonyl groups (Ji-Ye Jin et al.,1991) in the polymer. The broad absorption band of the polymer indicates a complex absorption caused by the products of broken pyrrole rings that initiate the branching and cross-linking of the polymer followed by various substitutions. Thus the plasma spectrograms can show secondary and tertiary amines that complicate the absorption in this range. Moreover, one cannot exclude the occurrence of the band at 1710cm-1 that, according to authors (Ji-Ye Jin et al.,1991) indicates the presence of carbonyl groups. This band is often observed in neutral or weakly doped forms of PPy, mainly due to their susceptibility to oxidation in air. The spectrum of

polymerization rate, which is confirmed by the higher rate of layer building up.

and CH3C6H4SO3-

). The oxidized

polymer is electro-conductive (incorporated dopants: Cl-

*3.3.2.2. Plasma polymerization method* 

**Figure 12.** FTIR-ATR spectra plasma synthesized polypyrrole, pyrrole plasma: 50W, 10min, p=0,05Tr. Sample 1-polymer without dopand, Sample 2 - polymer dopanded at plasma CH2J2 : 25W, 30min., p= 0,05Tr, Sample 3- polymer dopanded at J2 vapours, 30min

the polymer doped with iodine vapors contains an additional band at 1537cm-1, induced by the vibration of pyrrole ring, especially intensive in the polymer doped with crystalline iodine vapors. (Groenewoud et al. 2002) observed an increase in the intensity of peak 1520 cm-1 under the influence of iodine vapors, which is connected with the formation of a new CH2=J group in the reaction of iodine with radicals present in the surface layer of the plasma polymer.

The spectrum of the plasma polymer synthesized in the presence of nitrogen as a carrier of pyrrole proves how significant is the influence exerted by the process gas on the chemical polymer structure. This is particularly evident in the polymer synthesized for a longer time (the spectrum of polymer after a 1 h process – Figure 13). The FTIR-ATR spectrum of the plasma PPy at (500-1000) cm-1 contains numerous bands with a high absorption intensity that indicate the presence of primary amines (Kazicina.&Kupletska, 1976), and products of substituting chemical groups that were additionally formed in the polymer under the influence of the nitrogen plasma.

The absorption spectra obtained by the FTIR-ATR technique identify the chemical structure of PPy coatings and the structural changes that appear during changing the process parameters, such as pressure, power, type of doping agents, method of incorporating doping agents and the presence of process gas.

**Figure 13.** FTIR-ATR spectra plasma synthesized polypyrrole without dopands. Sample 1- plasma pyrrole 0,1Tr 10W, 15min, without processing gas, Sample 2- processing gas N2 and pyrrole p= 0,15Tr. 10W, 15min. Sample 3 - processing gas N2 and pyrrole p=0,15Tr 10W, 60min
