Search or add a thesis

Advanced Search (Beta)
Home > Synthesis and Characterization of Hyperbranched Polymers

Synthesis and Characterization of Hyperbranched Polymers

Thesis Info

Access Option

External Link

Author

Shabbir, Saima

Program

PhD

Institute

Quaid-I-Azam University

City

Islamabad

Province

Islamabad.

Country

Pakistan

Thesis Completing Year

2011

Thesis Completion Status

Completed

Subject

Chemistry

Language

English

Link

http://prr.hec.gov.pk/jspui/handle/123456789/1590

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727448816

Asian Research Index Whatsapp Chanel
Asian Research Index Whatsapp Chanel

Join our Whatsapp Channel to get regular updates.

Similar


The applications of macromolecules are widespread in the modern world and their utilities keep on increasing. Several significant developments in the field of polymeric materials engaged transfer of advantageous characteristics via control of polymer architecture. The interest in hyperbranched polymers (HBPs) stems from the ability to manipulate polymer composition to impart a particular set of traits. This basic research work on HBPs was driven by curiosity and charisma of these extremely elegant and intricate architectures. The present thesis aimed to fabricate HBPs in a one-pot method using new monomers synthesized in this work. All the newly synthesized monomers were subjected to FTIR, 1H, 13 C NMR spectroscopy and elemental analysis. The next goal was to utilize commercially available monomers in the facile synthesis to different families of HBPs. The reactions were stopped before gelation by the optimization of polymerization conditions. A three pronged strategy to HBP was pursued and in each specific strategy AB2, A2 + B3 and 2A2 + CBB′, the shell chemistry of the HBPs was employed to tailor desirable properties. Initially, a novel AB2 monomer, 6-hydroxy-2,4-bis(4′-nitrobenzamide)pyrimidine (NAL), was synthesized and successfully polymerized to hyperbranched polyamide-ethers (HBPAEs), which was subsequently end modified. Afterward, new trifunctional monomers, 1,3,5-tris(4''-hydroxyphenylcarbamoyl)benzene (THPCB), 1,3,5-tris(3'',4''- carboxyphenyl)benzene trianhydride (TAn), and 1,3,5-tris(4′- aminophenylcarbamoyl)benzene (TAPCB) were designed, synthesized and efficiently polymerized to hyperbranched polyamide-esters (HBPAE), hyperbranched polyester- imides (HBPEI) and hyperbranched polyamides (HBPAs) respectively, via the polymerization of A2 and B3 monomers without gelation. In these cases a dilute A2 solution was added slowly to a dilute B3 solution to prepare HB samples in the absence of gelation. A new 2A2 + CBB′ approach was undertaken where an A2C dimer was formed initially which can be considered as a new A2B type of monomer. Further reaction among A2C molecules resulted in the formation of hyperbranched polyamide-esters (HBPAEs) containing pyrimidine moieties. Complete structural 1 elucidation of the ensuing HBPs was carried out using FTIR, H and i 13 C NMR spectroscopic analyses. Additionally, all the prepared HBPs were characterized for qualitative solubility test, inherent viscosity, molar mass, thermal stability, glass transition temperature (Tg) and crystallinity. Structure-property correlations were established and it was observed that properties depended on end functionality. The degree of branching (DB) determined for HBPs based on the 2A2 + CBB′ approach was found to be >60 % and 41-56 % for the AB2 and A2 + B3 systems. Molar masses were determined using GPC which showed that the prepared HBPs had moderate Mw values. Thermal analyses for different HBPs systems showed that aliphatic HBPs were less thermally stable and had values of Tg lower than aromatic ones. HBPs contain a distinct multiplicity of peripheral functionalities which offer sites for additional chemical modification or as templates for non-covalent intermolecular interactions. Modification of the end groups in the prepared HBPs was carried out using different modifiers and complete modification was achieved proving that reactive terminal functionalities were easily accessible. The modified polymers displayed good solubility in different organic solvents. The properties of HB systems were compared with their linear analogues based on the same backbone structure. Accordingly, solution viscosity measurements exhibited that HBPs had lower solution viscosity, enhanced solubility and predominantly amorphous character compared to their linear analogues of comparable molar masses. Tg evaluation of HBP samples of different systems were carried out and showed that our HB systems demonstrated a lower Tg than their linear counterparts. Intermolecular hydrogen bonding between pyrimidine nitrogens and the amide NH groups of adjacent molecules provided the basis for material uniqueness. In addition, pyrimidine moieties played a vital role in producing outstanding thermal properties of HBPs; therefore, pyrimidine rings influenced the structural and material characteristics of these HBPs. Future prospects and potential applications of these HBPs are also envisaged.
Loading...
Loading...

Similar Books

Loading...

Similar Chapters

Loading...

Similar News

Loading...

Similar Articles

Loading...

Similar Article Headings

Loading...

سروجنی نائیڈو

مسز سروجنی نیڈو
افسوس ہے کہ ہماری قومی عمارت کا ایک اور ستون گرگیا اور ۲؍ مارچ کو مسز سروجنی نیڈو ہم سے رخصت ہوگئیں وہ عورت تھیں مگر اپنے اوصاف اور خصوصیات میں بہتیرے مردوں سے بڑھ کر تھیں، وہ انگریزی زبان کی نازک خیال شاعرہ، سحرطراز خطیبہ، سیاسیات کی ماہر، جنگ آزادی کی سرفروش سپاہی اور ہندومسلم اتحاد کا عملی نمونہ تھیں، انھوں نے آزادی کی جنگ میں مردوں کے دوش بدوش قیدوبند کی مصیبتیں جھیلیں، وہ فرقہ ورانہ جذبات سے بلند اور صلح کل تھیں، ان کا دل بڑا وسیع تھا، اس میں مسلمانوں کے لئے بھی جگہ تھی، مسلمانوں کے ساتھ ہمیشہ ان کے دوستانہ تعلقات رہے، اور اس فرقہ ورانہ دور میں بھی ان کے خیالات اور طرزعمل میں کوئی تبدیلی نہیں ہوئی تھی، ہندو مسلمانوں کے بعض اختلافی مسائل میں ان کے ذاتی خیالات حکومت کی پالیسی سے مختلف تھے، جن کو وہ صاف طریقہ سے ظاہر نہ کرسکتی تھیں، لیکن ان کی جھلک ان کی تقریروں میں نظر آجاتی تھی، وہ مغربی تعلیم یافتہ تھیں، ان کی ساری زندگی سیاسی میدان میں گزری، اس کے باوجود ان میں نسوانی اور مشرقی خصوصیات موجود تھیں، دل میں نسوانی مہرومحبت، طبیعت میں خلق و مروت، مزاج میں شگفتگی و خوش اخلاقی اور تہذیب و معاشرت میں مغربی آب و رنگ کے ساتھ مشرقی روح جھلکتی تھی، وہ اپنے طرز عمل سے ہندو مسلمان دونوں میں مقبول تھیں اور دونوں کا اعتماد ان کو حاصل تھا، اس لئے ان کی موت دونوں کا قومی حادثہ ہے، ہوا کا رخ دیکھتے ہوئے اب ایسی شخصیتوں کا پیدا ہونا بظاہر مشکل معلوم ہوتا ہے۔ (شاہ معین الدین ندوی، مارچ ۱۹۴۹ء)

 

أنموذج مقترح لقيادة مٌديري المدارس التغيير التربوي بسلطنة عُمان في ضوء بعض النماذج المُعاصرة

هدفت الدراسة الحالية إلى وضع أنموذج لقيادة مٌديري المدارس التغيير التربوي بسلطنة عُمان في ضوء بعض النماذج المُعاصرة، واتبعت الدراسة المنهج الوصفي، كما استخدمت نظرية تحليل المضمون في تحليل الوثائق في جمع البيانات والمعلومات. وتوصلت نتائج الدراسة إلى وضع أنموذج لقيادة مٌديري المدارس التغيير التربوي بسلطنة عُمان تكون من سبعة مراحل هي: الإيمان العميق بضرورة التغيير، وتشكيل فريق إدارة التغيير، ونشر ثقافة التغيير، ووضع خطة للتغيير، وتنفيذ التغيير، وتقويم التغيير والاحتفال بالنجاحات، والمٌتابعة والتغذية الراجعة المٌستمرة.

School Principal As a Strategic Leader: A Case-Study of a Private Sector School in District Chitral in Khyber Pakhtunkhawa Kpk Pakistan

School leadership plays a significant role in determining the levels and quality of school improvement process and its outcomes. The position of the school principal is of a door keeper to change that means how he receives the guests and what are the arrangements to welcome and how to please the guests. The school culture, practices and structure mainly revolve around the principals’ qualities, specifically in the private educational systems. The educational reforms and the fast moving technological era demand that the school leaders can only survive if they have strategic leadership qualities. They also require a strong vision for the institution. To achieve this vision, there should be a strong mission with strategic working styles and measures. The leaders should have the vision, the ability to share the vision with people inside as well as outside the organisation and inspire them to work jointly to accomplish the vision. Strategic leaders are those who have different thinking powers than the ordinary leaders and far-sighted lenses and thought processes to any endeavor. They scan the current position of the institution with respect to its internal and external environment, anticipate change proactively, set goals and objectives, align the organisation’s culture to these goals and negotiate across a wide breath of stakeholders for the survival of the organisation and its continuous improvement. They reflect on the strategies used for improvement and sustain the change in the complex and uncertain changing context. The purpose of the study is to explore and understand the principal’s role as a strategic leader. It also aims at understanding the role of the principal’s practices and position with futuristic lens. Moreover, to understand the principal’s powers to compete in a competitive situation in rural private context and the strategies used to sustain in the education market. The study employed the exploratory case study method selecting one school in the rural context of Chitral, Khyber Pakhtunkhawa (KPK), Pakistan. Qualitative data gathering strategies, namely; document analysis, observations, semi-structured and focus group discussions were made use of. The data were categorised and classified on the basis of the themes focusing on the principal’s practices and functions. The study findings reveal that the principal’s role is essential for strategic development in schools and strategic planning is fundamental to move towards the strategic direction. Strategic role of the principals is important for the educational development in far-flung rural areas. This study may help educational