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Synthesis and Characterization of Biodegradable Amphiphilic Block Copolymer Containing Polycarbonates

Thesis Info

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External Link

Author

Rubina, ,

Program

PhD

Institute

University of Karachi

City

Karachi

Province

Sindh

Country

Pakistan

Thesis Completing Year

2018

Thesis Completion Status

Completed

Subject

Chemistry

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/12976/1/Rubina%20Abdul%20Karim_Chem_2018_UoK_PRR.docx

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727440348

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Aliphatic polycarbonates are a newly emerging class of synthetic biodegradable polymers which are gaining attention due to their applications in biomedical fields including bond fixation, artificial skin, suture filaments, ligature clamps, devices for controlled drug release, bioresorbable prostheses, etc. Aliphatic polycarbonates possess several advantages compared to polyesters (other synthetic biodegradable polymers) that includes their resistance to acidic hydrolysis, thermal and hydrolytic stability, slow degradation rate and non-acidic degradation products. Most widely employed monomer for synthesis of aliphatic polycarbonate is trimethylene carbonate, a six membered cyclic carbonate, and its derivatives. Five-membered cyclic carbonates are not given much attention despite their huge potential as building blocks of biodegradable polymers. Polymerization of five-membered cyclic carbonates is associated with fractional decarboxylation during polymerization that leads to presence of ether linkages alongside targeted carbonate linkages. The demand of polycarbonates is significantly increasing due to their applications in various fields that inspired the improvement of synthesis methods. In this context, ethylene carbonate and propylene carbonate (five-membered cyclic carbonates) are polymerized in this study by ring-opening polymerization in the presence of sodium stannate trihydrate as a catalyst. Comprehensive microstructural analysis of the polymers was conducted by advanced one-dimensional (1H, 13C, DEPT-135o, & DEPT-90o) and two-dimensional nuclear magnetic resonance (NMR) techniques (COSY, TOCSY, HSQC & HMBC). The analysis revealed the co-existence of carbonate and ether units in polymer chain. Conversion and average ratio of carbonate to ether linkages of the polymer chains is quantified by 1H-NMR. Molar mass progression was evaluated by size exclusion chromatography. Selectivity of polymerization of both monomers with regard to polymerization speed, molar mass augmentation and relative ether to carbonate content as a function of polymerization conditions (such as temperature, monomer to initiator ratio, polymerization time and catalyst concentration) are evaluated. The polymers synthesized by ROP of ethylene carbonate and propylene carbonate are named as poly(ethylene ether-carbonate) and poly(propylene ether-carbonate), respectively. Furthermore, novel amphiphilic biodegradable di- and tri-block copolymers based on ethylene carbonate and propylene carbonate as hydrophobic segment while using methoxy poly(ethylene glycol)s and poly(ethylene glycol)s of varying molar masses as macro-initiator, were synthesized. Earlier elution of block copolymer from macro-initiator in size exclusion chromatography (SEC) indicated the successful synthesis of the block copolymers. Ratios of both types of blocks are varied systematically. Liquid chromatography at critical conditions for both hydrophilic and hydrophobic blocks are established to analyze the individual block length of non-critical blocks, and presence or absence of free critical blocks in the samples. Liquid chromatographic critical conditions of polymer synthesized by ROP of ethylene carbonate and propylene carbonate, poly (ethylene ether-carbonate) and poly(propylene ether-carbonate) respectively, were established for the first time. The established chromatographic critical points of PEG, PEEC and PPEC successfully tracked presence of homopolymers along with estimation of individual block lengths of the block copolymers. The synthesized biodegradable block copolymers can open new possibilities for modern drug delivery systems due to slow degradation rate and non-acid biodegradation products of polycarbonates.
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مولانا منت اﷲ رحمانی

حادثۂ وفات
ماہِ مارچ ۱۹۹۱ء میں ملّتِ اسلامیہ کواپنے دو۲عظیم رہنما عالمِ دین کے حادثۂ وفات سے دوچار ہونا پڑا۔
امیر شریعت بہار حضرت مولیٰنا منت اﷲ رحمانی اور میرٹھ شہر کے مشہور عالمِ دین، اسلامی مصنف حضرت مولیٰنا قاضی زین العابدین تھوڑے سے آگے پیچھے وقفہ میں انتقال فرماگئے۔اناﷲ وانا الیہ راجعون ۔
دونوں ہی ملّتِ اسلامیہ کی عظیم وبرگزیدہ ہستیاں تھیں۔حضرت مولیٰنا منت اﷲ رحمانیؒ نے ہندوستانی مسلمانوں کی مذہبی خدمت کرنے کے لیے اپنے مرحوم عالمِ دین والد مولیٰنا محمدعلی مونگیری سے ورثہ پایاتھا۔جس طرح مولیٰنا محمدعلی مونگیریؒ نے مسلمانانِ ہندکی تعلیم و تربیت کے لیے انتھک کوشش کی اور ندوۃ العلماء لکھنؤ کوجن لوگوں نے ایک تصور سے حقیقت بننے میں مدد دی ان میں مولیٰنا محمد علی مونگیریؒ کانام سر فہرست ہے۔مسلمانوں کی خدمت میں وہ جی جان سے لگے رہے جُٹے رہے۔اسی طرح ان کے لائق و ہونہار صاحبزادے اور بعد میں مِلّتِ اسلامیہ ہند کے غازی ومجاہد مولیٰنا منت اﷲ رحمانی نے مسلمانانِ ہند کی ہر طرح خدمت ورہنمائی کی۔مسلم پرسنل لاء بورڈ میں حضرت مولیٰنا مفتی عتیق الرحمان عثمانی ؒ کی رفاقت ورہنمائی میں بڑا اہم کردار نبھایا اور حضرت مفتی عتیق الرحمن عثمانیؒ کے انتقال کے بعد انہوں نے ان کے مشن کو ان کے بتائے ہوئے رہنما اصولوں کے تحت ہی آگے بڑھانے میں کوئی دقیقہ فروگزاشت نہیں کیا۔وہ دارالعلوم دیوبند کی مجلس شوریٰ کے بھی ممبر تھے۔مسلمانوں کی کئی فلاحی انجمنوں سے بھی ان کاربط وتعلق تھا۔
بقول معاصر ’’قومی آواز‘‘ مولیٰنا منت اﷲ رحمانیؒ کی وفات حضرت مولیٰنا مفتی عتیق الرحمان عثمانیؒ کی وفات کے بعد یہ دوسرا بہت بڑا صدمہ ہندوستان کے مسلمانوں کو پہنچا ہے اوراس کمی کو پورا کرنا آسان نہ ہوگا ۔۷۹؍ سال کی عمر پائی۔
[اپریل ۱۹۹۱ء]

The Circumstances Where the Quantum of Punishment Prescribed by Islam for Certain Crimes Can Be Reduced or Enhanced

The crime of theft if committed in unavoidable circumstances like extreme hunger or famine, Hadd punishment shall remain suspended. A crime of Zina if committed in a situation where the life of a woman is in danger because of hunger or thirst and she committed Zina to acquire food items or drinking water to save her life, she will be exonerated from the charges of Zina. In the light of Quranic injunctions, the punishment of a slave girl, if she committed Zina, is half as compare to independent women and the punishment for the wives of the Holy Prophet for committing the crime of fawahish or disobedience (Nushuz), is double as compare to other women. 4. Contrary to this principle, if a respectable person committed crimes under Tazir, he deserves lesser punishment or mere admonition in the light of tradition of the Holy Prophet: (Pardon the wrong done by the nobles of the society”.5. For awarding the punishment of Rajm, if the condition of Ihsan is fulfilled, he/she will be killed by stoning. According to Shiah Imamiah, Allama Rasheed Raza and others, when a person who is once married but due to divorce or separation, is living alone or miles away from his wife and not in a position to enjoy her company. If such person committed Zin┐, he or she will not be awarded the punishment of stoning.6. In the light of tradition, it is not allowed to award death punishment except the following three circumstances. Firstly, if a person, being a Mohsan, committed Zina, . Secondly, after accepting Islam, if a person converted to other religion. Thirdly, death punishment can be awarded in retaliation of murder committed

Fabrication and Study of Photovoltaic Devices Using Macrocyclic Organic Semiconductors

During the last decade, different structures of photovoltaic (PV) cells fabricated from organic semiconductors have drawn tremendous economic and scientific interest due to their high optical absorption efficiency, low fabrication cost, lightweight, high mechanical flexibility and continuous growth of their power conversion efficiencies. Bulk heterojunction organic solar cells can be fabricated by simple processing techniques, such as, screen printing, spin casting, etc., and, therefore, are potential candidates for the mass production of flexible and cost-effective devices. In this dissertation, based on the soluble macrocyclic organic semiconductors 5,10,15,20- tetraphenyl-21H,23H-porphine zinc (ZnTPP) and copper (II) tetrakis (4-cumylphenoxy) phthalocyanine (Tc-CuPc) bulk heterjunction structures of ITO/PEDOT:PSS/ZnTPP:PCBM/Al and ITO/PEDOT:PSS/Tc-CuPc:PCBM/Al were fabricated employing spin casting and vacuum thermal evaporation techniques. The effect of donor to acceptor (D:A) mass ratio was investigated on photovoltaic properties of the ZnTPP:PCBM BHJ solar cell and the optimum D:A ratio was identified. Effect of the thickness and surface morphology of the active layer on the photovoltaic properties of this porphyrin-fullerne BHJ was also studied and the optimum active layer thickness was identified. Bulk and hybrid-bilayer heterojunctions of copper (II) tetrakis (4- cumylphenoxy) phthalocyanine (Tc-CuPc) and vanadyl 2,9,16,23-tetraphenoxy- 29H,31H-phthalocyanine (VOPcPhO) heterojunctions were also fabricated. Temperature dependent electrical properties of these devices and optical performance of the Tc- CuPc:PCBM bulk heterojunction was also investigated. Macrocyclic semiconductors e.g. metallo-phthalocyanines (MPcs) and metallo- porphyrins (MPPs), are restricted to dry processing techniques due to their insolubility in common organic solvents. Thus MPcs and MPPs are used in typical thermally evaporated donor-acceptor bi-layered solar cells. The performance of bi-layer solar cells is low due to small exciton diffusion length; only the excitons generated within 10 nm from the D/A interface are expected to contribute to photocurrent. This issue is resolved in BHJ architecture, in which the D-A interfacial area is distributed throughout the volume (bulk) viiiof the active layer. In other words the D-A interface is brought near to the exciton generation site. Soluble versions of MPcs and MPPs can be helpful to study their opto- electronic characteristics in BHJ solar cell architecture. In BHJ architecture there is a lot of flexibility and ease for rapid research e.g. changing solvent, varying concentration, using different D to A mass ratios, changing active layer thicknesses by spin coating at different speeds, incorporating different exciton-blocking layers etc. A lot of variations can be studied in a very short time and with less cost. However, as more and more research groups start studying soluble macrocyclic organic semiconductors in BHJ solar cells, further efficiency improvements and availability of new soluble macrocyclic materials are worthwhile. Since the microstructure of bulk heterojunction layer is strongly dependent on the donor to acceptor (D:A) mass ratio, an optimum D:A ratio improves device performance by improving the charge separation, transport and collection process. As one aspect of this research work, porphyrin-fullerne BHJ solar cells with ITO/PEDOT:PSS/ZnTPP:PCBM/Al structure were fabricated with different D:A mass ratios and their optical parameters were measured both under simulated solar spectrum AM 1.5G and monochromatic illuminations. The active layer thicknesses were extracted from their respective optical reflection and transmission measurements using average absorption coefficient. Scanning electron microscope (SEM) image of the device cross section was studied to verify layer thicknesses and examine the quality of layers. Effect of thermal annealing on performance of some devices was also studied. Incident photon- to-current conversion efficiency (IPCE) spectra at different D:A ratios was determined. On basis of the measured optical parameters such as fill factor FF, open circuit voltage V OC , short circuit current density J SC , and power conversion efficiency η , the optimum D:A ratio was identified. Maximum IPCE value of 21% was obtained for D:A ratio of 1:9 which lead to PCE of 0.21% which was 36 times better than a previously reported value in which C 60 was used as acceptor. Also incorporating PCBM as the acceptor instead of C 60 improved the open circuit voltage (V OC ) for all the D:A ratios. The reason for high V OC is greater difference between the ZnTPP HOMO and PCBM LUMO . Furthermore the 1:9 devices showed consistency in optical parameters when reproduced.