İyonlaşabilen gruplar içeren N-izopropilakrilamid kopolimer jellerinin sentez ve karakterizasyonu
Başlık çevirisi mevcut değil.
- Tez No: 75451
- Danışmanlar: DOÇ. DR. CANDAN ERBİL
- Tez Türü: Yüksek Lisans
- Konular: Kimya, Chemistry
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1998
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Kimyagerlik Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 82
Özet
ÖZET Bu çalışmada 2 adet N-izopropilakrilamid (NIPAAM) homopolimer jeli ile, 6 adet N- izopropilakrilamid-akrilik asit (NIPAAM-AA), 6 adet N-izopropilakrilamid itakonik asit (NIPAAM-IA) ve 4 adet N-izopropüakriIamid-maleik asit (NTPAAM-MA) kopolimer jelleri sentezlenmiştir. Kopolimer jellerinin sentezlerinde %1, 5 vel0 mol oranında komonomerler kullanılmıştır. Başlatıcı (K2S2O8) konsantrasyonu sabit tutulmak üzere, homo NIPAAM jelleri ile %1 komonomer içeren kopolimer jelleri iki farklı hızlandırıcı ( N, N, N', N- tetrametiletilendiamin ) konsantrasyonunda oda sıcaklığında sentezlenerek, hızlandırıcı miktarının jellerin fiziksel özellikleri üzerindeki etkisi incelenmiştir. Ayrıca, %5'lik kopolimer jelleri başlatıcı ve hızlandırıcı miktarları sabit tutularak, üç farklı çapraz bağlayıcı ( N,N- metilenbisakrilamid) konsantrasyonunda sentezlenmiş ve çapraz bağlayıcı konsantrasyonunun jellerin fiziksel özellikleri üzerinde etkisi incelenmiştir. Düz zincirli ve çapraz bağlı NIPAAM homopolimerleri ile %10'luk kopolimerlerin FTIR spektrumlan çekilerek, düz zincirli ve çapraz bağlı polimerlerin yapıları karşılaştırmıştır. Elde edilen homopolimer ve kopolimer jelleri ile sabit sıcaklıkta, suda şişme deneyleri yapılmış ve bu deneylerin sonuçlarından örneklerin kütlece ve hacimce yüzde şişmeleri, çapraz bağlar arası sayıca ortalama molekül ağırlığı ve birim hacim başına etkin çapraz bağ konsantrasyonları hesaplanmıştır. Sentezlenen homo ve kopolimerik jellerin 20-70°C sıcaklık aralığında sudaki faz geçişleri gözlenerek, şişme denge oranlan hesaplanmıştır. xi
Özet (Çeviri)
SYNTHESIS AND CHARACTERIZATION OF N-ISOPROPYLACRYLAMIDE COPOLYMER GELS CONTAINING IONIZABLE GROUPS SUMMARY A gel is a form of matter intermediate between a solid and a liquid. It consists of polymers, or long chain molecules, crosslinked to create a tangled network and immersed in a liquid medium. The properties of the gel depend strongly on the interaction of these two components (liquid and network). The liquid prevents the polymer network from collapsing into a compact mass, the network prevents the liquid from flowing away. Depending on the chemical composition and physical stimuli such as temperature, type of the solvent, pH, ionic composition, electrical fields, etc., gels vary in consistency from viscous fluids to fairy rigid solids, but typically they are soft and resilient or, in a word, jellylike. Polymer gels are known to exist in two distinct phases, swollen and collapsed. Between these two phases, a transition can occur; either continously or discontinously via volume transition. For a gel to undergo the phase transition, it is necessary that polymers interact with each other through both repulsive and attractive interactions and the balance of competing interactions has to be modified by various effects. The phase behavior of a gel, therefore, crucially depends on the nature of interactions between polymers. With respect i to temperature dependence, three types of phase transition have been reported. The first is the thermoswelling type, or expansion with temperature; the second is the thermoshrinking type, or collapse with temperature; and the third is the 'convexo' type, a mixture of two types described above. Thermoswelling gels can contain either hydrophobic monomers mainly dimethyl siloxane, styrene-divinyl benzene or hydrophilic monomers such as acrylarnide, acrylic acid and methacrylic acid. On the other hand, the main examples of thermoshrinking gels are composed of especially hydrophobic monomers like N-isopropylacrylamide (NIPAAM), N-methylacrylamide and N, N-diethylacrylamide. Hydrogels are most common used gels in industry. They are waterswellable gels and their capacity to absorb water is enormous. Hydrogels find application in food industry (as thickening agents, etc.), in pharmaceuticals (as controlled release preparates, etc.), agriculture and related fields (in controlled release of moisture, fertilizers, pesticides, etc.), technical and electronic instruments (as a protector from corrosion and short circuits, etc.), bioengineering (in biomolecular immobilization), biomedicine (as artifical organs,etc), veterinary, medicine, photographic technology xiiand as an adsorbent for removal of some unwanted agent in environmental application. Besides the use of these artificial gels, there are many natural gels in human body, such as materials of the cornea and blood-vessel walls, the surface cover of stomach, intestine and lung. Homo NIPAAM and especially its copolymeric gels undergo the phase transition near the temperature of the body. For this reason, these gels can be used in human body for biochemical and pharmaceutical purposes. In this work, NIPAAM homo and copolymer gels were synthesized. The chosen comonomers were acrylic acid (AA), itaconic acid (IA) and maleic acid (MA). Gels prepared by free radicalic polymerization in aqueous solution at room temperature. The used initiator, cross-linker and accelerator were K2S2O8, BIS and TEMED, respectively. Gelation was performed in glass tubes of 3.60 mm. inner diameter. FTIR spectra of linear and cross-linked NIPAAM and %10 IA containing NIPAAM copoymers were obtained and compared. Investigation of swelling equilibria and phase transitions of the samples were performed by swelling studies both gravimetrically and volumetrically. From the results of gravimetric swelling studies, the percentage of mass swelling %S(m) was calculated from the following relation: where mo is the weight of the dried gel and m is the weight of swollen gel at any time. The percentage volume swelling, %S(v) is given by: where pp and ps are the polymer and solvent (water) densities, respectively. Volumetric swelling results were used to calculate the swelling ratio of the equilibrium gel diameter to the original diameter do as follows: V/V0 = (d/d0)3 (3) One of the most important structural parameters characterizing crosslinked polymers is Mc, the average molecular weight between crosslinks, which is directly related to the crosslinking density. The magnitude of Mc significantly affects the physical and xiiimechanical properties of crosslinked polymers and its determination has great practical significance. Equilibrium swelling values are used to determine K7C according to the theory of Flory-Rehner: Where Mc is the average molecular weight of the polymer between crosslinks, Vi is the molar volume of the solvent, pp is the polymer density, v2ni is the volume fraction of polymer in the swollen gel, x1 is the Flory-Huggins interaction parameter between solvent and polymer and v2° is the volume fraction of the network after preparation. V1, pp, V2m and V20 values were calculated from the results of the swelling experiments. The %\ value were calculated from the following equation: Xi = [ ln( 1 - v2m) + v2m ] v2m“2 (5) The calculated %i values of homopolymeric and copolymeric gels were obtained 0.52 and 0.50-0.51 (according to the comonomer mol ratio), respectively. vc, effective crosslink concentration per unit volume was also calculated for each samples: ve= pp/Mc (6) Preparation conditions of homo and copolymeric gels were given in Table 1. 1 8 Gel samples two of which were homo NIPAAM were synthesized by using (1-10%) AA, I A and MA comonomers with the same initiator (K2S208) concentration. During the preparation, two different accelerator (TEMED) and three different cross-linker (BIS) concentrations were used. The results calculated from the swelling measurements by using gravimetric methods were given in Table 2. From the results of the swelling experiments, it has seen that %S(m),%S(v) and Mc values increased by increasing mol ratios of comonomers in the gels, while ve values decreased. These comonomers contain hydrophilic groups (-COOH). For this reason, hydrogen bonding can occur and then, gel swells. If the number of -COOH groups increases, more hydrogen bonding occurs. Both IA and MA contains two -COOH groups; so, their swelling values of copolymer gels are higher than NIPAAM-AA copolymer gels synthesized in the same conditions.In comparision with NIPAAM-IA gels, the swelling and Mc values of NIPAAM-MA copolymer gels are higher. It is known that MA is a stronger acid than IA (pK1 ma=1.9I, pK 1 1a=3.85). For this reason, the ionization degree of MA is higher, then, this attidude results in a rise in the electrostatic interaction in the gel and gel swells. When the accelerator concentration used in the synthesis increased, the number of the chains increases, shorter chains forms and the crosslinking density decreases. So, when the quantity of TEMED is increased, %S(m), %S(v) and Mc values increased, while ve values decreased. However, during the synthesis, if we increase the concentration of BIS, it results in a rise in crosslinking density, then, pores is getting enlarged and the swelling of the gel increases. Swelling equilibrium ratio variation with temperature were obtained from the volumetric measurements. Figure 1 and 2 examplified these curves. Phase transition of a gel is a result of a competitive balance between a repulsive force that acts to expand the polymer network such as electrostatic interactions between the same charged groups and an attractive force that acts to shrink the network such as van der Waals, hydrophobic interaction and hydrogen bonding. In comparison with NIPAAM gels, the phase transition temperatures of NIPAAM copolymer gels are higher. Moreover, when the comonomer mol ratio increases, the temperature of the phase transition increases. Because, these comonomers contains ionizable groups which result in an electrostatic interaction in the network. This interaction is a repulsive force. It acts to expand the gel and prevents the shrinking of the gel. At higher temperatures, attractive forces cause the phase transition of the gel. IA and MA copolymer gels which contain two -COOH groups undergo the phase transition at higher temperatures than AA does. Because, the number of -COOH groups in IA and MA copolymer gels are higher and it results in a higher electrostatic interaction in the network. When we compare MA and IA copolymer gels, we observe that phase transition temperature of MA is higher because of its higher acidity. We observed a swelling in the networks which contains high comonomer mol ratios or synthesized with a high quantity of BIS below the phase transition temperature. As it can be explaned, in these samples, the electrostatic interaction is high and it causes a swelling in the network before phase transition temperature. In the temperature of phase transition, the attractive forces effects the network strongly; so gel swells. xvTable 1. Preparation conditions of the gels. [K2S208] =0.0405 g”T=23°C (Room temperature) Table 2. %Seq(m), %Seq(v), Mc,ve values of the gels obtained from gravimetric measurements of the swelling experiments. XVIT *C 60- 55- 50 45 40 35- 30- 2S O A A O A & o© a Ort A 0 û 2 AO o A 01 ~>“ 1 1 - ı - ıııı 0.2 0J 0.4 0.6 08 1.0 20 3.0 40 50 V/V0 Figure 1. Swelling equilibria for gels of NIPAAM synthesized by using (A) 0.008 g TEMED, (4) 0.013 gTEMED. T °C 70- 65”60- 55 50- 40 35- ÛO Ad ? a o û A O o A 30 ID D 01 -, 1 1 1 1 - I I I A O p 1 1 1 - I - 1-1 - 0.2 0.3 0.5 0.8 10 2.0 3.0 4.0 6.0 V7V0 Figure 2. Swelling equilibria for 5% containing copolimeric gels of (4) AA, and (?) MA. TA XVII
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