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Synthesis and Characterization of Novel Azomethine Based Polyimides

Thesis Info

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Author

Iqbal, Rubbia

Program

PhD

Institute

Government College University

City

Faisalabad

Province

Punjab

Country

Pakistan

Thesis Completing Year

2016

Thesis Completion Status

Completed

Subject

Chemistry

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/12972/1/Rubbia_Iqbal_Chemistry_GCU_Faisalabad_2015_04.01.2016.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727456865

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In this research project thirty three new polyimides (PI-1 – PI-33) were synthesized from two series of diamines by polymerization with commercially available dianhydrides, pyromellitic dianhydride (PMDA), 4,9,10-perylenetetracarboxylic acid dianhydride (PD) and 3,3’,4,4’-benzophenonetetracarboxylic acid dianhydride (BD). Two series of diamines having azomethine (Series-I) and azomethine with ether linkage (Series-II) with aliphatic substituent’s like –CH3, -OH, -OCH3, -Cl were synthesized. The polyimides were synthesized by a conventional two steps method which involves the ring opening polyaddition at room temperature followed by the imidization either by thermal or chemical methods. All the synthesized diamines and polyimides were characterized by using different techniques like elemental analysis, TGA, FT-IR and 1H-NMR. All the spectral data were found in good agreement with the proposed structures of polyimides. These synthesized polyimides were also subjected for the study of organosolubility, inherent viscosity, molecular weight measurement, moisture absorption, thermal behaviour, crystallinity and thermodynamic parameters. The organosolubility of the synthesized polyimides were checked in different solvents qualitatively. The majority of the polyimides were found soluble in common polar aprotic solvents like m-cresol, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), N,Ndimethylacetamide , tetrahydrofuran (THF) and sulphuric acid at room temperature as well as some of them were soluble on heating. The improvement in the oraganosolubility of the polyimides might be due to the presence of aliphatic substituents and ether linkages in the backbone of the polyimides which reduced the chain-chain interactions and hence enhance the chances of penetrating solvent molecules into polyimide chain. The inherent viscosities were found in the range of 0.59 – 0.85 dLg-1 indicating the moderate to higher molecular weight of polyimides. Weight average molecular weight (Mw) and number average molecular weight (Mn) of the polyimides were found in the range of 59,000 – 86,000 gmol-1 and 36,000 - 53,000 gmol-1 respectively. Moisture absorption capacity of the polyimides was found in the range of 0.38 - 0.89%. The moisture absorption capacity of the polyimides is greatly influenced by the chemical structure of polyimides. The polyimides exhibited excellent thermal properties having glass transition temperature g in the range of 220 – 292°C and the 10% weight loss temperature were above 400°C without significant weight losses up to 360°C. The polyimides PI-23 – PI-33 having 3,4,9,10-perylenetetracarboxylic acid dianhydride (PD) showed better thermal stability due to the rigid structure of dianhydride. Most of the polyimides displayed amorphous pattern in X-ray diffraction analysis. The polyimides of 3,3’4,4’-benzophenonetetracarboxylic acid dianhydride (BD) and pyrromellitic dianhydride (PMDA) units with azomethine linkage having aliphatic moieties diamines displayed semi-crystalline pattern. The values of thermodynamic parameters , activation energy, enthalpy and entropy fall in the range of 31– 54 kJmol-1, 29 – 52 kJmol-1 and 0.15 to 0.26 kJmol-1K-1 respectively. Due to improved solubility and better thermal stability these polyimides could be applicable for high performance polymeric materials applications like high temperature application, as heat resistant polyimide materials, in the synthesis of plastic materials, in organic materials, in magnetic materials, etc.
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تبصرے

تبصرے
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Productivity of Sunflower Hybrids As Influenced by Sulphur-Nitrogen Nutrition and Varying Plant Population

The present research work was carried out to investigate the effect of sulphur- nitrogen nutrition and varying plant population on productivity of sunflower hybrid at the agronomic research Area, University of Agriculture Faisalabad. Two years field oriented research experiments were conducted for 2006 and 2007. In the first experiment sunflower hybrid Hysun-33, was subjected to four sulphur level (0, 40, 80, 120 Kg ha -1 ) and four nitrogen levels (0, 40, 80,120Kg ha -1 ). The experiment was laid out in RCBD factorial with three replications. In the second experiment three sunflower hybrid viz., FH-331 (early maturing), SF187 (medium maturing) and Hysun-33 (late maturing) were tested at three row spacing (45cm, 60cm and 75cm).The variation in agronomic and physiological characteristics of sunflower was analyzed with varying levels of sulphur and nitrogen. During both years of study sulphur and nitrogen application @ 80 and 140 Kg ha -1 produced maximum achene yield (3167-3000Kg ha - 1 ), which was the out come of better yield contributing attributes (higher leaf area, maximum crop growth rate, better light interception, dominant head size, higher 1000- achene weight).On an average maximum oil yield of 1090 and 1121 Kg/ha were obtained with the application of 80 and 140 Kg ha-1 sulphur and nitrogen, respectively. An increase in protein contents (%) was experienced with increasing sulphur levels, and vice versa with enhancing the nitrogen levels. Radiation utilization efficiency for dry mater and grain was also significantly increased with higher nitrogen rate and sulphur application @ 80 Kg ha -1 . Computation of benefit cost ratio (BCR) revealed that the highest BCR 2.38 was also pertinent to the same treatment in sunflower are 80 and 140 Kg/ha -1 , respectively. In the second experiment the hybrid Hysun-33, which was a late maturing hybrid, not only recorded highest leaf area index, but also experienced maximum crop growth rate, highest plant height, greatest number of achenes, and maximum achene yield. On an average Hysun-33(late maturing type) produced significantly higher achene yield (3033-2888Kg ha -1 ), planted at 60cm apart rows, and SF-187(medium maturing hybrid) harvested maximum achene yield(2783-2740Kg ha - 1 ), when sown at 45 cm wider rows. The early maturing (FH-331,a local hybrid) responded well to the row distance of 45 cm and produced highest achene yield of xv2633-2533 Kg ha -1 . Although, with increasing rows spacing from 45-75cm, the sunflower crop resulted in larger heads, possessing more achenes per head, and heavier individual achene, but the boost in yield of the hybrids FH-331 and SF-187 with decreasing the row spacing (increasing plant population) was principally associated with more achene number per unit area, higher leaf area index and maximum crop growth rate. Therefore, it is concluded that under tropical to semi-arid region like the experimental area (located at 73.09 o East longitude and 31.25 o North latitude and at an altitude of 184 m), the best sulphur and nitrogen doses to get maximum achene yield. Highest achene yield 3084 kg ha -1 was recorded where sulphur was applied at the rate of 80 kg ha -1 for along with 140 kg ha -1 nitrogen. Computation of benefit cost ratio (BCR) revealed that the highest BCR 2.38 was also pertinent to the same treatment in sunflower are 80 and 140 Kg/ha -1 , respectively. Regarding hybrids and their planting density, late maturing hubris like Hysun-33 should be planted at 60 cm apart rows with plant to plant distance of 22.5. Medium and early maturing sunflower hybrids may be preferred to be sown at 45 cm apart rows with plant to plant distance of 22.5 cm.