اثر ید مولکولی و بازدارنده‌ رادیکالی 4-ترشیوبوتیل کتکول بر پلیمرشدن رادیکالی استیرن

نوع مقاله: پژوهشی

نویسندگان

تهران، دانشگاه تربیت مدرس، دانشکده مهندسی شیمی، گروه مهندسی فرایندهای پلیمریزاسیون، صندوق پستی 114-14115

چکیده

اثر ید مولکولی بر وزن مولکولی و توزیع وزن مولکولی پلی­‌استیرن تولید شده در پلیمرشدن رادیکالی استیرن بررسی شد. پلیمرشدن رادیکالی استیرن شروع شده با آغازگر 2،׳2-آزوبیس(ایزوبوتیرونیتریل) (AIBN) در دمای 70 درجه سلسیوس و در مجاورت مولکول ید انجام شد. از آزمون‌های رنگ‌نگاری ژل تراوایی (GPC) و طیف‌بینی رزونانس مغناطیسی پروتون (1H NMR) برای شناسایی پلیمرها استفاده شد. نتایج این آزمون‌ها شامل تبدیل واکنش، وزن مولکولی متوسط و توزیع وزن مولکولی با نتایج به­ دست آمده برای پلیمرشدن رادیکالی استیرن شروع شده با آغازگر AIBN در دمای مشابه، در غیاب مولکول‌های ید مقایسه شد. نتایج نشان داد، ید اثر بسزایی بر وزن مولکولی و توزیع وزن مولکولی پلیمر نهایی سنتز شده دارد و به­‌خوبی قابلیت کنترل پلیمرشدن را با سازوکار پلیمرشدن رادیکالی انتقال ید معکوس دارد و به تولید پلیمری با وزن مولکولی l10600g/molو توزیع وزن مولکولی 1.3 منجر شود. با توجه به اهمیت دوره‌ القا در پلیمرشدن رادیکالی انتقال ید معکوس، دوره‌ القا با افزایش دما تا 120 درجه بسیار کوتاه‌ ­تر شد و گونه‌های تشکیل شده طی این دوره به کنترل بهتر وزن مولکولی منجر شدند. همچنین، با توجه به اینکه مولکول‌های ید در ابتدا به‌­عنوان بازدارنده‌ رادیکالی عمل می‌کنند، نقش وجود بازدارنده‌ رادیکالی 4-ترشیوبوتیل کتکول در کنار مولکول‌های ید در پلیمرشدن رادیکالی استیرن شروع شده با آغازگر AIBN بررسی شد. مشاهده شد، وجود بازدارنده‌ رادیکالی، مانع از مصرف مولکول‌های ید به ­وسیله رادیکال‌های حاصل از تجزیه آغازگر شیمیایی و تشکیل آلکیل هالید طی دوره‌ القا می‌شود.

کلیدواژه‌ها


عنوان مقاله [English]

Effects of Molecular Iodine and 4-tert-Butylcatechol Radical Inhibitor on the Radical Polymerization of Styrene

نویسندگان [English]

  • Mojtaba Bozorg
  • Mahdi Abdollahi
  • Mohammad Ali Semsarzadeh
Polymer Reaction Engineering Department, Faculty of Chemical Engineering, Tarbiat Modares University, P.O. Box: 14115-114, Tehran, Iran
چکیده [English]

The presence of molecular iodine was studied in relation the molecular weight and molecular weight distribution of polystyrene, produced by radical poly merization. Radical polymerization of styrene initiated by 2,2׳-azobisisobutyronitrile (AIBN) was performed at 70°C in the presence of molecular iodine. The synthesized polymers were characterized by gel permeation chromatography (GPC) and proton- nuclear magnetic resonance (1H NMR) techniques. The results of these reactions including conversion data, number-average molecular weight and molecular weight distribution were compared with those obtained for styrene radical polymerization initiated by AIBN at the same temperature in the absence of molecular iodine. It was found that the presence of iodine had a profound effect on the molecular weight and its distribution in the produced polystyrene. This was attributed to the ability of iodine to control the polymerization of styrene initiated by AIBN via reverse iodine transfer polymerization (RITP) mechanism. The polymer produced by this method had a molecular weight of 10600 g/mol with a molecular weight polydispersity index of 1.3. Due to the importance of induction period in reverse iodine transfer radical polymerization, increasing the temperature to 120°C during the induction period resulted in shorter induction periods and the produced species led to better control of the molecular weight. Also, due to the role of iodine molecules as a radical inhibitor, the presence of a secondary radical inhibitor, i.e. 4-tert-butylcatechol, along with the iodine was investigated in radical polymerization of polystyrene initiated by AIBN. It was observed that the secondary radical inhibitor prevented the consumption of the iodine molecules by the radicals produced from decomposition of the AIBN initiator; therefore, alkyl halides were not produced during the induction period.

کلیدواژه‌ها [English]

  • radical polymerization
  • styrene
  • inhibitor
  • controlled polymerization
  • reverse iodine transfer polymerization
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