Phthalonitrile resins are high temperature thermosetting polymers, which are considered ideals materials for marine, aerospace, and electronic applications. The synthesis of phthalonitrile monomers with self-catalyzing nature and with large processing window – defined as the temperature between the melting temperature of the monomer and the gelation temperature of the polymer network–, are gaining much more importance because of ease in processability and high thermal stability. In the present study, some novel phthalonitrile resins were synthesized using ortho- linked phthalonitrile monomers and self-catalyzing phthalonitrile monomers with different linkages such as: ether, imide-ether, and amide-ether between the reactive ends. All the synthesized monomers were characterized by spectroscopic techniques such as FT-IR, 1 H-NMR and 13 C-NMR. FT-IR indicated absorption peaks around 1522 and 1355 cm -1 and around 1010 cm -1 indicated the formation of triazine and phthalocynine rings (heterocyclic rings formed as a result polymerization) respectively after post curing. The thermal analyses were carried using DSC, TGA, DMA, and Rheometery. DSC and rheometric studies showed that the monomers with ortho linkages have low melting point and high crosslinking temperature. In self-catalyzed monomers, the monomers having amino group at ortho position or 1,2-linked (ortho) monomers have broad processing window. The complex viscosity (η*) was very low (<1 Pa.s) in between melting and the crosslinking temperature, which is highly suitable for resin transfer molding, resin infusion molding, and filament winding. TGA studies revealed that the resin synthesized from the monomer with heterocyclic ring shows high thermal stability and residual mass (char yield). The thermal stability of the polymer having ether or imide-ether linkages are nearly the same but more than the polymer having amide-ether linkage, indicating the effect of crosslinking density and structural changes. DMA measurements showed that storage muduli (E'') and glass transition temperature (Tg) enhance with the increase of curing temperature. These meaurements also indicated that the polymers having imide-ether and amide-ether linkages have higher storage moduli than the polymers have only ether linkages.
پروفیسر شیخ عبدالقادر سرفراز (پونا) ناسک (بمبئی) کے ایک خط سے جو مرحوم کے چھوٹے بھائی نے مجھے لکھا تھا یہ معلوم کرکے بڑا تاسف ہوا کہ میرے چالیس برس کے دوست پروفیسر شیخ عبدالقادر سرفراز نے پونہ میں اپنے مکان کا شانہ حق میں ۱۰؍ دسمبر ۱۹۵۲ء کو ساڑھے نو بجے انتقال فرمایا، اس کے بعد مرحوم کے بڑے صاحبزادے ڈاکٹر شیخ عبدالحق ایم، اے۔ پی، ایچ، ڈی پروفیسر اردو فارسی (بمبئی) کی اطلاع سے اور بہت سی باتیں معلوم ہوئیں، یہ بھی معلوم ہوا کہ مرحوم کو بڑھاپے اور شیخوخت کے ضعف کے سوا کوئی خاص مرض نہ تھا، بصارت سے معذور ہوچکے تھے، ایک ہفتہ سے ضعف بڑھتا جاتا تھا، ڈاکٹروں کے معائنہ سے قلب اور اعضائے رئیسہ توانا پائے گئے، حواس آخر تک بجا تھے، سوا نو بجے خود آنکھیں بند کرلیں لب ہل رہے تھے، غالباً کلمہ پڑھ رہے تھے، ۱۵ منٹ کے بعد یعنی ساڑھے نو بجے صبح کو اس دنیائے فانی سے سفر اختیار کیا۔ ۱۹؍ جولائی ۱۸۷۹ء پیدایش کی تاریخ تھی، بہتر (۷۲) برس کی عمر پائی، مرحوم کا خاندان دراصل یوپی کا باشندہ تھا، غدر کے ایام میں بمبئی کی طرف نکل گیا، مرحوم کے والد شیخ سرفراز ڈاکٹر تھے، انہوں نے ناسک کو اپنا وطن بنایا لیکن مرحوم کی عمر کا بڑا حصہ پونہ اور بمبئی میں گزرا ۱۹۰۲ء میں بمبئی یونیورسٹی سے ایم، اے پاس کیا اور غالباً ان کا خاص موضوع فارسی تھا، اس زمانہ میں ایک شریف ایرانی فاضل پروفیسر مرزا حیرت بمبئی یونیورسٹی میں فارسی کے مسندنشین صدر تھے، ان کا غیر معمولی فضل و کمال تمام بمبئی میں مسلم تھا، مرحوم شیخ عبدالقادر کو فارسی کا ذوق انہی کی صحبت سے حاصل ہوا، چنانچہ مرزا حیرتؔ کی انہوں نے مختصر سوانح عمری بھی لکھی ہے اور مجلس میں اکثر ان کے فضائل...
Allama Jarullah Al-Zemakhshari was a great scholar, linguistic, and a man of letters. His book, Tafseer al- Kasshaaf ‘an- Haqaiq et-Tanzeel, is one of the most famous and universally acknowledged book in which he has discussed Arabic grammar, literature and rhetoric. It is an extremely important Tafseer and is considered a primary source by all great scholars. It is famous for its deep linguistic analysis, rhetoric and grammatical issues. Allama Al-Zemakhshari has cited many poets’ poetry both from Pre-Islamic era and Islamic era as a proof to support his arguments. In this article the researcher has cited Al-Zemakhshari’s attitude towards Quoting the Poetry of Mowalldeen (postclassical poets) and to point out those places where he has quoted Mowalldeens’ (postclassical poets) poetry for proof in his Tafseer Al-kasshaff.
Aromatic polyimides are materials of scientific and commercial interest due to their high thermal stability, excellent mechanical strength and stiffness at elevated temperatures, chemicals and radiation resistance etc. Owing to such worthy combination of aforementioned properties, these polymers have broad spectrum of applications in modern industries. These exceptional properties of polyimides are mainly dependent on their chemical structures hence, can be attuned as required. The prime objective of the dissertation was to tailor the properties of polyimides. The task was accomplished by implementing three different methodologies: i) structural modifications of monomers (diamine/dianhydride), ii) copolymerization, and iii) nanocomposite engineering. With respect to structural modifications, eight new diamine monomers were synthesized successfully having systematic and comparable variations in their structures. Their design involved the considerations of structure rigidity (having different contents of aromatic and aliphatic moieties) and catenation (different positioning of amino groups). These synthesized diamines were condensed with three different dianhydrides for the development of twenty four novel polyimides. Another series comprising of fifteen polyimides was prepared by using five structurally related commercial diamines to explore the influence of different side or pendant groups on the properties of resulting polyimides. The dianhydrides used in the project were selected to study the impact of different bridging groups, with respect to tailoring of properties. The new copolyimides were synthesized by simultaneous reaction of two different diamines (one of the synthesized diamine + 4,4ʹ-methylenedianiline) with the same dianhydride. The polyimide nanocomposites were engineered via incorporating Al2O3 and ZnO nanoparticles within the polyimide matrix at different loading levels.The spectroscopic techniques like FTIR and NMR (1H, 13C) were used for structural elucidations of dinitro compounds, diamine monomers, polyimides and copolyimides. The single crystal X-ray diffraction analysis of the synthesized dinitro and diamine compounds validated their proposed structures from the spectroscopic data and provided valuable information about their spatial orientations and inter/intra-molecular attractions. The incorporation of nanoparticles (Al2O3 and ZnO) inside the polyimide matrix was verified by WAXRD analysis while SEM and TEM microscopic techniques disclosed their homogenous distribution throughout the matrix. The properties of polyimides, copolyimides and polyimide nanocomposites were evaluated by dynamic and isothermal TGA (nitrogen and air atmospheres), DMTA (dynamic mechanical thermal analysis) and WAXRD studies. Polyimides displayed significantly high thermal stability as their decomposition started around 400 °C and experienced a relatively small weight loss up to the temperatures of 450-500 °C. Isothermal TGA revealed that the synthesized polyimides displayed substantially high thermal endurance at 400 °C i.e. capable to withstand elevated temperatures for long time. Their thermal performance was affected considerably as a function of monomer architect. The thermal stability/endurance of polyimides was also tailored by changing catenation of amino functionality and substituting different side or pendant groups in the diamine monomers. The nature of bridging group in the dianhydrides influenced the thermal behavior of obtained polyimides. The incorporation of 4,4ʹ-methylenedianiline (MDA) as co-monomer within the backbone of polyimides (copolymerization) resulted in substantial enhancement of their thermal stability and high temperature durability. The nanocomposites engineering also modified the properties of polyimide. The glass transition temperatures of polyimides exhibited an increasing trend with the methyl substitution on the benzene rings of MDA or replacement of its methylene hydrogens with -CF3 and 9-fluorenylidene moieties. However, it was decreased upon ethyl exchange on the benzene rings. The polyimides displayed storage modulus (Eʹ) above one GPa up to the temperature around 250 °C. The Al2O3 and ZnO nanoparticles increased the glass transition temperature of the polyimide matrix in concentration dependent manner up to the optimum level. WAXRD analysis revealed the semicrystalline to amorphous morphology of polyimides depending upon the monomer structure. The polyimides derived from 3,3ʹ,4,4ʹ-benzophenonetetracarboxylic dianhydride (BTDA) and para-catenated diamines displayed semi-crystalline behavior. However, it was decreased upon copolymerization and changed to amorphous while going from: para to meta/ortho or BTDA to ODPA/6FDA analogues (ODPA = 4,4ʹoxydiphthalic anhydride and 6FDA = 4,4''-hexafluoroisopropylidenebisphthalic anhydride).