The influence of antioxidant and post-synthetic treatment on the properties of biodegradable poly(butylene succinate)s modified with poly(propylene oxide)

Abstract

Novel poly(ester-ether)s based on poly(butylene succinate) (PBS) as the hard segments and 30 mass % of poly(propylene oxide) (PPO) as the soft segments were synthesized with varying amount of the antioxidant (N,N'-diphenyl-p-phenylenediamine, DPPD). The influences of the addition of DPPD and the impact of post-synthetic treatment by precipitation on the molecular structure, thermal and physical properties, as well as on the storage stability of the biodegradable aliphatic copolyesters, were investigated. The structure and composition of the copolymers were determined by means of 1H-NMR spectroscopy. The molecular weight and polydispersity of the poly(ester-ether)s were evaluated from solution viscosity and GPC measurements. The thermal properties and stability were evaluated, respecttively, by means of DSC and non-isothermal thermogravimetry in an inert nitrogen atmosphere. The biodegradability potential of the polymers was studied in hydrolytic and enzymatic degradation tests with Candida cylindracea lipase by monitoring the weight loss of polymer films after incubation. The weight losses of the samples increased with time and were in the range from 1 to 5 mass % after 4 weeks. GPC analysis confirmed that there were changes in the molecular weight of the copolyesters during both hydrolytic and enzymatic degradation tests, leading to the conclusion that the degradation mechanism of poly(butylene succinate)s modified with PPO occurred through surface erosion and bulk degradation.

U okviru ovog rada sintetisani su novi poli(estar-etri) na bazi poli(butilen sukcinata) (PBS) kao tvrdih segmenata i 30 masenih % poli(propilenoksida) (PPO) ugrađenih u meke segmente, bez i u prisustvu antioksidansa N,N′-difenil-p-fenilendiamina (DPPD). Izučavao se uticaj antioksiodansa DPPD kao i načina izdvajanja polimera, odnosno pretaložavanja na strukturu i veličinu molekula, termička i fizička svojstva kao i na stabilnost biodegradabilnih alifatskih kopoliestara. Struktura i sastav kopoliestara su provereni 1H-NMR spektroskopijom. Veličina molekula i raspodela veličina molekula sintetisanih poli(estar-etara) su određeni viskozimetrijom razblaženih rastvora i GPC analizom. Termička svojstva i termička stabilnost poli(estar-etara) su analizirana DSC i neizotermskom termogravimetrijom u inertnoj atmosferi azota. Biodegradabilni potencijal polimera je izučavan u ogledima hidrolotičke i enzimske degradacije u prisustvu lipaze Candida cylindracea prateći promene u masi polimernih filmova tokom inkubacije. Gubici su rasli sa vremenom i posle 4 nedelje su bili u opsegu od 1 do 5 masenih %. GPC analiza je potvrdila da postoje promene u molarnoj masi uzoraka i u ogledima hidrolitičke i enzimske degradacije na osnovu čega se može zaključiti da se mehanizam degradacije poli(estar-etara) na bazi PPO odvija kroz eroziju površine i degradaciju u masi.