Modification of chlorinated polypropylene via clickchemistry

In this thesis, different properties have been gained to commercially chlorinated polypropylene (PP-Cl) via copper (I)-catalyzed azide-alkyne cycloaddition "click" reaction (CuAAC). The first part of the thesis, graft copolymers from commercial chlorinated polypropylene (PP-Cl) possessing either poly(ethylene glycol) (PEG) or poly(ɛ-caprolactone) (PCL) are synthesized by copper (I)-catalyzed azide-alkyne cycloaddition "click" reaction (CuAAC). For this purpose, azido-functional polypropylene is prepared by nucleophilic substitution of chlorine groups of PP-Cl with azidotrimethylsilane-tetrabutylammonium fluoride. Whereas, the clickable alkyne end-functional PEG and PCL are independently synthesized by esterification reaction of poly(ethylene glycol) methyl ether with 4-pentyonic acid at room temperature and ring-opening polymerization of ε-caprolactone using stannous octoate as catalyst and propargyl alcohol as initiator. Finally, the corresponding graft copolymers, PP-g-PEG and PP-g-PCL, with different surface properties were successfully synthesized by CuAAC "click" reaction under mild condition. Spectral, chromatographic and thermal analyses at various stages prove the formation of desired polypropylene-based graft copolymers with well-defined properties. Furthermore, the water contact angle values of PP-Cl, PP-g-PEG and PP-g-PCL are found as 90o (±1), 78o (±1.8) and 83o (±2.1), respectively. The second part of the thesis, polypropylene possessing quaternary ammonium salt (PP-QAS) is synthesized by copper (I)-catalyzed azide- alkyne cycloaddition "click" reaction (CuAAC) starting from chlorinated polypropylene (PP-Cl). The antibacterial properties of obtained PP-QAS have been investigated on gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria. For this purpose, clickable azide functionality has been introduced into PP-Cl backbone by using azidotrimethylsilane (TMS-N3) - tetrabutylammonium fluoride solution (TBAF) system in THF (PP-N3). Independently clickable alkyne functionalized QAS is prepared by the reaction between 3-dimethylamino-1-propyne and benzyl bromide in the presence of triethyl amine (TEA). Finally, the polypropylene film containing quaternary ammonium salt (PP-QAS) is prepared by the successive CuAAC "click" reaction and solution casting method. The preparation of PP-QAS is monitored by FT-IR, 1H-NMR and DSC analyses at various stages. Based on antibacterial activity experiments, the PP-QAS coupons significantly inhibit both the growth of S. aureus and E. coli (p<0.05) compared to neat PP-Cl and control samples. The third of thesis, synthesis of fluorine containing polypropylene (PP-F) from chlorinated polypropylene (PP-Cl) via Cu(I) catalyzed Huisgen type 1,3-dipolar cycloaddition (CuAAC) and its water repellency properties are demonstrated. Initially, azido-functional polypropylene (PP-N3) is prepared by nucleophilic substitution of chlorine groups of PP-Cl with azidotrimethylsilane-tetrabutylammonium fluoride system. Independently, 2,2,3,3,4,4,5,5-octafluoro-1-pentanol is converted to clickable alkyne-functionalized fluorine compound (F-Al) by esterification reaction between its hydroxyl group and 4-pentyonic acid in the presence of N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine. The CuAAC reaction between PP-N3 and F-Al leads to corresponding PP-F under mild conditions. The chemical structures and surface properties of desired PP-F are characterized by FT-IR, 1H-NMR, DSC and contact angle analyses. Based on water contact angle (WCA) measurement, it is found that both PP-Cl and PP-N3 films have shown similar hydrophobicity and the Cl groups have not caused a significant decrease on the WCA value due to their slight amounts in the structure. Interestingly, the presence of hydrophilic ester groups coming from F-Al compound and triazole ring in the clicked PP-F provides to increase in the wettability of the films. Furthermore, the obtained PP-F has also shown hydrophobic behavior, however, a slight decrease in the WCA values is observed when compared to PP-Cl films. The last part of thesis, the syntheses of polypropylene-graft-poly(L-lactide) copolymers (PP-g-PLLAs) via copper (I)-catalyzed azide-alkyne cycloaddition ''click'' reaction (CuAAC) using azide side-chain functionalized polypropylene (PP-N3) and alkyne end-functionalized poly(L-lactide) (PLA-Alkyne) and their characterizations have been reported. Azido-functional polypropylene (PP-N3) and alkyne end-functionalized poly(L-lactide) (PLA-Alkyne) are first obtained by the reaction of PP-Cl with azidotrimethylsilane-tetrabutylammonium fluoride and ring openning polymerization (ROP) of L-lactide in the presence of tin(II) 2-ethylhexanoate as a catalyst and propargyl alcohol as an initiator, respectively. The CuAAC is then applied to azide and different feeding ratios of alkyne functional polymers to give PP-g-PLLAs that are characterized by FT-IR, 1H-NMR, GPC, DSC and WCA meauserements. The effect of the feeding ratio of PLA-Alkyne on the CuAAC reaction and graft copolymers properties are investigated. Wettability and thermal properties, and biodegredable behaviour of the graft copolymers are enhanced by increasing the molar ratio of PLA side chains on the PP main chain. The comparing PP-Cl, PP-g-PLA-1 (molar ratio of PLA-Alkyne is found as 82.7 %) and PP-g- PLA-2 (molar ratio of PLA-Alkyne is found as: 78.4%), the water contact angle dropped from 90o±1.0 to 81o±1.3 and 75o±1.6, suggesting a more hydrophilic nature of desired graft copolymers. On the other hand, systematically conducted biodegradation studies upon enzymatic degradation showed us that the PP-Cl, PLA-Alkyne, PP-g-PLA-1 and PP-g-PLA-2 samples lost about 4, 38.8, 13.6, 22.1% of its weight, respectively.