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Politetrahidrofuran makrobaşlatıcı ve mikroinimer sentezi ve reaksiyonları

Başlık çevirisi mevcut değil.

  1. Tez No: 55622
  2. Yazar: AYŞEGÜL BAŞKAN
  3. Danışmanlar: PROF.DR. YUSUF YAĞCI
  4. Tez Türü: Yüksek Lisans
  5. Konular: Kimya, Chemistry
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 1996
  8. Dil: Türkçe
  9. Üniversite: İstanbul Teknik Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: Belirtilmemiş.
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: 51

Özet

ÖZET Bu çalışmada öncelikle uç grupları modifıye edilmiş politetrahidrofuran (PTHF) polimerleri sentezlenmiştir. Azo-oksokarbenyum tuzu ve gümüşhekzafloraantimonat (AgSbF6) ile yaşayan katyonik polimerizasyon yöntemiyle elde edilen PTHF piridinyum N-oksit türevleri ile sonlandınlmıştır. N-alkoksi piridinyum tuzlarının, doğrudan veya dolaylı olarak aktif hale getirilmesiyle vinil monomerlerin serbest radikal polimerizasyonlannı başlatacak alkoksi radikallerinin üretimini sağladığı bilinmektedir. Elde edilen bifonksiyonel politetrahidrofuran makrobaşlatıcı, sıralı olarak fotokimyasal ve termal başlatma özelliğine sahiptir. Bir diğer makrobaşlatıcı olarak aynı yöntemle elde edilen yaşayan PTHF metakrilat anyonu ile sonlandınlmıştır. PTHF makroinimer, hem başlatma hemde monomer özelliğine sahip olduğundan, termal olarak homo ve metil metakrilat (MMA) ile kopolimerizasyonu yapıldı. Makroinimer ile MMA polimerizasyonu dallı ve çapraz bağlı MMA-THF blok kopolimerlerini vermektedir. vı

Özet (Çeviri)

SUMMARY TOE SYNTHESIS OF POLYTETRAHYDROFURAN MACROINITIATORS AND MACROMIMER AND THEIR REACTIONS Block copolymers find a very large number of disparate applications. They are used as thermoplastic elastomers, adhesives and sealants, surface modifiers and binders. Currently, block copolymer synthesis is a very active and expanding field. Various methods have been proposed and used for the synthesis of block copolymers. These methods are generally based on the sequential monomer addition in living systems and the use of macroinitiators. Polytetrahydrofuran macroinitiators were synthesized by means of cationic polymerization of tetrahydrofiiran, initiated by azo-oxocarbenium salt, followed by termination with pyridinium N-oxide derivatives. The resulting PTHF-macroinitiators possesses both a termally and photochemically labile group. It is well known that initiation of THF polymerization by oxo-carbenium salts is quantitative, rapid and proceeds by addition mechanism. Moreover, polymerization is considered to be living since it proceeds without chain transfer and termination reactions under closely controlled conditions. In this work, we have employed in situ generated azo-oxocarbenium salt initiator for the polymerization of THF according to reaction (1), which ensues incorporation of thermolabile functionality. The second functionality, photofunctionality was introduced by taking advantage of quantitative deactivation of this polymerization. The quenching the living ends of polymer with iV-oxides according to reaction (2) resulted in the formation of JV-Alkoxy pyridinium ion terminated polytetrahydrofurans. The structure of the resulting polymers was confirmed by ^H NMR, UV and GPC measurements. The results are summarized in Table 1. The *H NMR. spectrum of a typical 4 sample (Figure 1) exhibits signals in the range of 7-9 ppm corresponding to the aromatic protons of the pyridine ring in addition to characteristic PTHF signals. vuCH3 CH3 O C!-C-CH2-CH2-C-N=N-C-CH2-CH2-C-CI + 2AgSbF6 CN CN O CH3 CH3 9 II II II _ SbF;+C-CH2-CH2-C-N=N-C-CH2-CH2-C+ SbF6 + 2 AgCI | CN CN 2 O (1) O CH3 CH3 O.. C0+4(CH2)4-O^C-CH2-CH2-C-N=N-C-CH2-CH2-C-t_0^“CH2”CH2*T**«*- O -(CHj ^ O CN CN Synthesis of polytetrahydrofuran macroinimer Scheme 1 The macroinimers obtained were charactarized by ^H-NMR analysis and GPC measurements. The *H-NMR spectrum of a typical macroinimer in Figure 3 exhibits weak signals at 5,6 and 6,2 ppm corresponding to vinylic protons in addition to the characteristic PTHF signals. The molecular weight (Mn:22500), which was determined from the integration ratios, of the signals was in good agreement with that by the GPC method (Mn:21000). This result indicates that the macroinimer obtained by this method was highly pure and possesess two vinyl groups per macromolecule. Macroinimers were thermally homo and copolymerized with methylmethacrylate (MMA) in CH2CI2 at 60 °C. Macroinimers yielded only crosslinked products in the absence of MMA, since macroinimers possess both initiating and polymerizing functionalities. Polytetrahydrofuran macroradicals formed upon thermolysis react with polymerizable acrylate to the following reaction (Scheme 2). XI-AA. 5 (ppm) Figure 3. 1H-NMR spectrum ofPTHF-1 macroinimer Polymerization of MMA with macroinimers gave branched and crosslinked MMA-PTHF block copolymer. Soluble fraction of the products increased with increasing monomer concentration. Notably, a control experiment without PTHF macroinimer failed to produce any precipitable polymer after the same heating time at 60°C. Both soluble and crosslinked block copolymers possess PTHF segments. Notably, the percentage of PTHF segment is high in the crosslinked product whereas soluble polymers contain mainly PMMA segments. The precursor PTHF macroinimers dissolve in methanol at room temperature and precipitate at low temperature, i.e. 0°C. The temperature dependent solubility behaviour of low molecular weight PTHFs makes it possible to separate resulting block copolymers from precursor macroinimer. In Figure 5, the FT-IR spectrum of the soluble branched THF-MMA block copolymer exhibits bands characteristics of carbonyl group of PMMA at 1730 cm-* and of ether group of PTHF at 1 190 cm"1. XIICH3 6=CH, CH3 H2C=C o=6 ç=o A CH3 6=CH2 6=0 *vwu«ww«r( CH3 o=6 6 CH3 i 0=6 6 Mwwvw : PTHF segment Scheme 2 100 %T 3500 3000 2500 2000 1500 Wavenumber (cm-1) 1000 500 Figure 5. BR. spectrum of the soluble fraction of branched MMA-THF block copolymer xm

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