**5. Analysis of infrared spectroscopy in biomedical polymer material**

The key difference between medical polymer material and other polymer materials is that the former has both medical functionality and biocompatibility and resorts to chemical or physical means to achieve polymeric modification of polymer materials. Fourier Transform Infrared Spectroscopy (FT-IR) is an effective method to analyze polymer materials and its modification.

5.1 The transformation degree of dental composite resin after polymerization may directly affect the biological, chemical and mechanical strength. The most urgent problem in the application and development of the composite resin material is to remove various unfavorable factors that may affect solidification of the composite resin to maximize its transformation degree. FTIR spectroscopic technology may comprehensively study the polymerization of chemical curing and visible-light curing composite resin and the influences of various factors to the degree of polymerization as well as the relationship between transformation degree of the composite resin and the various indirect indicators. The existing study on FTIR indicates: Of different brands of dental composite resin available in market, the transformation degree of visible-light curing resin is superior to that of the chemical-curing resin; the double bond transformation degree and the mechanical properties of the resin have positive correlation with the contents of the catalyst and the reductive and have negative correlation with the contents of the inhibitors.

Application of Infrared Spectroscopy in Biomedical Polymer Materials 177

5.3 Another key focus of study is to use combined infrared spectroscopy and computer technology to make quantitative analysis of the chemical structure of the auxiliary materials added to the medical polymer, such as additive, adhesives and plasticizer. Spectrum subtraction technology can be used to identify the additives in the high polymer products. Medical infusion devices are made of conventional polymer material polyvinyl chloride (PVC) and 2-ethylhexyl phthalate (DEHP) is added to plasticize rigid polyvinyl chloride (PVC), with additive dosage of 40-60%. Study has verified that DEHP can enter human body through venous transfusion, respiratory tract and skin and bring damage to human health. This has become focus of academic research and disputes and has attracted attention from media. Though DEHP's toxicity and carcinogenicity has been fully confirmed in experimental animals, its adverse effect in human body is still controversial. Using infrared spectroscopy subtract technology to analyze PVC infrared spectrogram of PVC and the infrared spectrogram of plasticized PVC may determine the kernel of material construction of the plasticizer. FTIR spectrum subtraction may also be used in polymer end-group analysis,

polymer oxidation and degradation reaction analysis and inter-molecular analysis.

rigid PVC and PVC materials used in medical infusion equipment.

2865.51

2919.41

4000 2000

Fig. 5. Infrared spectrogram of PVC and DEHP

**5.4 Polymer materials in ophthalmology** 

30

40

50

60

%T

70

80

90

100

Below is the infrared spectra of traditional bis (2-ethylhexyl) phthalate (DEHP) plasticized

2358.76

Wavenumbers (cm-1)

Contact lenses are the most common polymer product in ophthalmology. The basic requirements for this type of materials are: ①excellent optical properties with a refractive index similar to cornea; ② good wettability and oxygen permeability; ③ biologically inert, degradation resistant and not chemically reactive to the transfer area; ④ with certain mechanical strength for intensive processing and stain and precipitation prevention. The common used contact lens material includes poly-β-hydroxy ethyl methacrylate, poly-βhydroxy ethyl methacrylate-N-vinyl pyrrolidone, poly-β-hydroxy ethyl methacrylate, Polyβ-hydroxy ethyl methacrylate - methyl amyl acrylate and polymethyl methacrylate ester-Nvinyl pyrrolidone, etc. The artificial cornea can be prepared by silicon rubber, poly methyl

477.41

617.12

688.12

964.24

1104.43

1244.40

1328.70

1644.90

1736.39

1430.57

5.2 As the polymer surface properties affect the cohesiveness, wettability and biocompatibility of the polymer and its actual application, the study focusing on improving polymer properties through polymer surface modification. The quantitative analysis of the polymer surface composition is the important basis for the property study. Attenuated total reflectance infrared spectroscopy (ART-FTIR) technology is one of the most effective methods to test the information of the material construction of the polymer surface without interference of the test samples. Just as transmission infrared spectrum, ATR-FTIR provides information [1-5] about chemical structure, three-dimensional structure, molecular orientation and hydrogen bond of the material. The existing study[6] uses attenuated total reflectance Fourier transform infrared spectroscopy (FTIR-ATR) to test the surface composition of polyethylene glycol/ polyethylene blends (PEG/PE) film. With the corresponding characteristic peak intensity ratio as the basis for the quantitative determination, ATR correction procedures, and NMR-FTIR correction equation[6~7] : Y=0.346 48-1.336 55X+1.268 37X2,, are used for quantitative analysis of the relative composition of the polyethylene glycol chain and the polyethylene chain on the blend surface to obtain a better result of the reproducibility and comparability. The quantitative analysis of the relative composition of polyethylene glycol chain and the polyethylene chain on the surface layer of the blend film is achieved through working curve method. See figure as below:

A. ATR spectrumwithout calibration; B. Corrected ATR spectrum; C. The difference spectrum between spectra A and B

Fig. 4. ATR spectra of blend of PEG (2000) and LLDPE

5.2 As the polymer surface properties affect the cohesiveness, wettability and biocompatibility of the polymer and its actual application, the study focusing on improving polymer properties through polymer surface modification. The quantitative analysis of the polymer surface composition is the important basis for the property study. Attenuated total reflectance infrared spectroscopy (ART-FTIR) technology is one of the most effective methods to test the information of the material construction of the polymer surface without interference of the test samples. Just as transmission infrared spectrum, ATR-FTIR provides information [1-5] about chemical structure, three-dimensional structure, molecular orientation and hydrogen bond of the material. The existing study[6] uses attenuated total reflectance Fourier transform infrared spectroscopy (FTIR-ATR) to test the surface composition of polyethylene glycol/ polyethylene blends (PEG/PE) film. With the corresponding characteristic peak intensity ratio as the basis for the quantitative determination, ATR correction procedures, and NMR-FTIR correction equation[6~7] : Y=0.346 48-1.336 55X+1.268 37X2,, are used for quantitative analysis of the relative composition of the polyethylene glycol chain and the polyethylene chain on the blend surface to obtain a better result of the reproducibility and comparability. The quantitative analysis of the relative composition of polyethylene glycol chain and the polyethylene chain on the surface layer of the blend film

is achieved through working curve method. See figure as below:

A. ATR spectrumwithout calibration; B. Corrected ATR spectrum;

Fig. 4. ATR spectra of blend of PEG (2000) and LLDPE

C. The difference spectrum between spectra A and B

5.3 Another key focus of study is to use combined infrared spectroscopy and computer technology to make quantitative analysis of the chemical structure of the auxiliary materials added to the medical polymer, such as additive, adhesives and plasticizer. Spectrum subtraction technology can be used to identify the additives in the high polymer products. Medical infusion devices are made of conventional polymer material polyvinyl chloride (PVC) and 2-ethylhexyl phthalate (DEHP) is added to plasticize rigid polyvinyl chloride (PVC), with additive dosage of 40-60%. Study has verified that DEHP can enter human body through venous transfusion, respiratory tract and skin and bring damage to human health. This has become focus of academic research and disputes and has attracted attention from media. Though DEHP's toxicity and carcinogenicity has been fully confirmed in experimental animals, its adverse effect in human body is still controversial. Using infrared spectroscopy subtract technology to analyze PVC infrared spectrogram of PVC and the infrared spectrogram of plasticized PVC may determine the kernel of material construction of the plasticizer. FTIR spectrum subtraction may also be used in polymer end-group analysis, polymer oxidation and degradation reaction analysis and inter-molecular analysis.

Below is the infrared spectra of traditional bis (2-ethylhexyl) phthalate (DEHP) plasticized rigid PVC and PVC materials used in medical infusion equipment.

Fig. 5. Infrared spectrogram of PVC and DEHP

#### **5.4 Polymer materials in ophthalmology**

Contact lenses are the most common polymer product in ophthalmology. The basic requirements for this type of materials are: ①excellent optical properties with a refractive index similar to cornea; ② good wettability and oxygen permeability; ③ biologically inert, degradation resistant and not chemically reactive to the transfer area; ④ with certain mechanical strength for intensive processing and stain and precipitation prevention. The common used contact lens material includes poly-β-hydroxy ethyl methacrylate, poly-βhydroxy ethyl methacrylate-N-vinyl pyrrolidone, poly-β-hydroxy ethyl methacrylate, Polyβ-hydroxy ethyl methacrylate - methyl amyl acrylate and polymethyl methacrylate ester-Nvinyl pyrrolidone, etc. The artificial cornea can be prepared by silicon rubber, poly methyl

Application of Infrared Spectroscopy in Biomedical Polymer Materials 179

study shows the conformation changes of PVC films with different thermal histories in heating process. Meanwhile, in FTIR measurement, the sample subjected to heat treatment below Tg temperature occurred sudden change of conformation in the temperature range corresponding to enthalpy absorption peak of differential scanning calorimetry (DSC).

Fig. 7. Spectrum of Orthokeratology Using Gas Permeable Rigid Contact Lens

clarified through analysis of infrared spectrogram of tissues or cells.

[3] Bergberiter D E, Srinivas B. Macromolecules, 1992, 25: 636.

[5] Francis M, Mirabella J R. Appl. Spectrosc. Rev., 1985, 21: 45.

[4] Lee K W, Kowalczyk S P, Shaw J M. Macromolecules, 1990, 23: 2097.

FTIR is becoming widely used in the field of medical polymer materials, especially for quantitative analysis of the material properties. At present, the study on application of infrared spectroscopic technology or combined application of IR spectrum with other technologies in polymer material, to be still growing. With rapid development of scientific technology, the research in IR spectrum is further deepened. IR spectrum is not only widely used in polymer materials but is also widely used in pharmaceuticals, foods and environmental science. The gradually improved infrared detection method may be used on vivo analysis of pathological tissue and greatly contribute to the rapid and accurate diagnosis of the diseases. Meanwhile, the disease mechanism and progression maybe

[1] Yang Qun, Wang Yi-lin, Yao Jie, et al. Spectroscopy and Spectral Analysis, 2006, 26(12):

[2] Jiang Zhi, Yuan Kai-jun, Li Shu-fen, et al. Spectroscopy and Spectral Analysis, 2006, 26(4):

**6. Prospect** 

**7. References** 

2219.

624.

acrylate, poly-casein or other thin films. The main body of the artificial lens can be made of polymethacrylate. The researchers have attached increasingly great importance to the qualitative analysis of polymer materials for this kind of medical equipments. As explicitly specified in YY0477-2004 "Orthokeratology Using Gas Permeable Rigid Contact Lens", infrared spectrum analysis is adopted to determine the components of the lens materials. The following drawing is the infrared spectrum analysis of this material: point 2961cm-1 is the methyl characteristic peak of methyl acrylate; points 1104 cm-1 and 1046 cm-1 are characteristic absorption peaks of siloxane, points 1730 cm-1,1227 cm-1 and 1199 cm-1 are ester peaks of methyl acrylate; points 893 cm-1 and 7556 cm-1 are the structure characteristic peaks of polymethacrylate; also it is worth knowing that carbonyl peak on point 1769 cm-1 is the characteristic peak of fluoro-alkylated methyl acrylate.

Fig. 6. Infrared spectrogram of PVC

5.5 The innovation of instrument performance and the development of computer application technology provide possibility for combined use of the previous stand-alone analysis instruments. The combined use of various types of instruments has greatly improved the accuracy and reliability of the analysis and testing results. With combination use of thermogravimetric analysis and IR spectrum and other analytical methods in recent years, thermogravimetric analysis is increasingly playing an important role in study of thermal behavior in chemical materials. In comparison with traditional thermogravimetric analysis method, TGA-IR spectrum combined analysis can directly and accurately determine the various physical-chemical change during the heating proves and identify the chemical composition of decomposition or degradation products during the during the weight loss process. Thus, it has been a key experimental method in studying thermostability and thermal decomposition (degradation) process of various inorganic, organic and polymer materials and proves a promising prospect in respect of thermal performance analysis of the materials. As Fourier transform infrared spectrometer is of high noise-signal ration and high precision, it may detect the slight intensity change and frequency shift of the infrared bands in the sample before and after the heat treatment. Thus to provide structural differences of polymer film for three different thermal stages of high molecular polymer, from high-elastic state slow cooling, high-elastic state quenching to heat treatment below temperature Tg. The study shows the conformation changes of PVC films with different thermal histories in heating process. Meanwhile, in FTIR measurement, the sample subjected to heat treatment below Tg temperature occurred sudden change of conformation in the temperature range corresponding to enthalpy absorption peak of differential scanning calorimetry (DSC).

Fig. 7. Spectrum of Orthokeratology Using Gas Permeable Rigid Contact Lens
