کوپلیمرشدن رادیکالی وینیل ایمیدازول و وینیل فسفونیک اسید: ارتباط توزیع توالی-دمای انتقال شیشه‌ای کوپلیمرها

نوع مقاله : پژوهشی

نویسندگان

تهران، دانشگاه تربیت مدرس، دانشکده مهندسی شیمی، گروه مهندسی فرایندهای پلیمریزاسیون، صندوق پستی 143-14115

چکیده

فرضیه: کوپلیمرشدن موفق‌ترین و قدرتمند‌ترین روش برای اعمال تغییرات اصولی در خواص پلیمر است. سودمندی و کارایی کوپلیمرشدن از یک طرف با پژوهش‌های بنیادی ارتباط خواص-ساختار و از سوی دیگر به‌وسیله محدوده گسترده‌ای از کاربردهای تجاری مشخص می‌شود. تعیین ساختار کوپلیمر (ترکیب کوپلیمر و توزیع توالی مونومر) یکی از چالش‌های اصلی برای پیش‌بینی خواص کوپلیمر و ارتباط میان ساختار و خواص است.
روش‌ها: هوموپلیمرهای پلی(1-وینیل ایمیدازول) و پلی(وینیل فسفونیک اسید) به‌ترتیب در مجاورت α´،α-آزوبیس ایزوبوتیرونیتریل (AIBN) و α´،α-آزودی‌ایزوبوتیرآمیدین دی‌هیدروکلرید (AIBA) به‌عنوان آغازگر سنتز شدند. کوپلیمرهای پلی(1-وینیل ایمیدازول-وینیل فسفونیک اسید) در نسبت‌های مختلف مولی از مونومرها در خوراک اولیه با روش پلیمرشدن رادیکال آزاد رسوبی در حلال دی‌متیل فرمامید (DMF) در دمای C°80 تهیه شدند. ساختار و ریزساختار پلیمرها با روش‌های طیف‌سنجی بررسی شد. در ادامه، دمای انتقال شیشه‌ای هومو و کوپلیمرها با آزمون‌های گرماسنجی پویشی تفاضلی (DSC) و تجزیه گرمایی دینامیکی-مکانیکی (DMTA) اندازه‌گیری شد.
یافته‌ها: نسبت‌ واکنش‌پذیری کومونومرهای 1-وینیل ایمیدازول و وینیل فسفونیک اسید با استفاده از روش Kelen-Tudos توسعه یافته و نتایج آزمون 1H NMR به‌ترتیب 078/0 و 870/0 به‌دست آمد. نسبت واکنش‌پذیری کومونومرها تمایل آن‌ها به تشکیل کوپلیمر متناوب را نشان داد. ریزساختار کوپلیمرها شامل توالی دوتایی مونومرها با استفاده از نسبت واکنش‌پذیری کومونومرها و معادله‌های نظری تعیین شد. سپس، دمای انتقال شیشه‌ای کوپلیمرها با استفاده از توالی‌های محاسبه‌شده و معادله Barton پیش‌بینی شد که تطابق بسیار خوبی با مقادیر تجربی نشان داد و مشخص شد، ریزساختار کوپلیمرها اثر مهمی بر دمای انتقال شیشه‌ای آن‌ها دارد.

کلیدواژه‌ها


عنوان مقاله [English]

Radical Copolymerization of Vinylimidazole and Vinylphosphonic Acid: Sequence Distribution-Glass Transition Temperature Relationship in Copolymers

نویسندگان [English]

  • Mojtaba Farrokhi
  • Mahdi Abdollahi
Department of Polymer Reaction Engineering, Faculty of Chemical Engineering, Tarbiat Modares University, PO. Box: 14115-114, Tehran, Iran
چکیده [English]

Hypothesis: Copolymerization is the most successful and powerful method for making systematic changes in polymer properties. The utility of copolymerization is exemplified on the one hand by fundamental investigations of structure-property relations and on the other hand by the wide range of commercial applications. The elucidation of copolymer structure (copolymer composition, monomer sequence distribution) is the major concerns for the prediction of copolymer properties and the correlation between structure and properties.
Methods: Homopolymers of poly(1-vinylimidazole) and poly(vinylphosphonic acid) were synthesized in presence of α,α´-azobisisobutyronitrile (AIBN) initiator for the former, and in presence of α,α´-azodiisobutyramidine dihydrochloride (AIBA) initiator for the latter. Poly(1-vinylimidazole/vinylphosphonic acid) copolymers at various molar ratios of monomers in initial feed were obtained by precipitation free radical polymerization in dimethyl formamide (DMF) as solvent at 80°C. The structure and microstructure of the polymers were investigated by spectroscopy methods. Afterwards, the glass transition temperatures of the homo- and copolymers were measured by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA).
Findings: The reactivity ratio of 1-vinylimidazole and vinylphosphonic acid comonomers was obtained using extended Kelen-Todus method and the results of 1H NMR were 0.078 and 0.870, respectively. The reactivity ratio of the comonomers indicated their tendency to form an alternative copolymer. The microstructure of the copolymers, i.e. the diad sequence of monomers, was determined using the reactivity ratio of the comonomers and the theoretical relationships. Then, the glass transition temperature of the copolymers was predicted utilizing calculated sequences and Barton's relation that showed good agreement with the experimental values, and it was found that the microstructure of the copolymers had a significant effect on their glass transition temperature.

کلیدواژه‌ها [English]

  • vinylphosphonic acid
  • 1-vinylimidazole
  • copolymerization
  • microstructure
  • microstructure-properties relationship
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