The effect of polar solvents on the synthesis of poly(urethane-urea-siloxane)s

Abstract

Segmented poly(urethane-urea-siloxanes) (PUUS) based on 4,4'- methylene diphenyl diisocyanate-ethylene diamine (MDI-ED) hard segments and hydroxypropyl-terminated poly(dimethylsiloxane) (PDMS, Mn = 1000 g mol-1) soft segments were prepared under various experimental conditions. The copolymers with constant molar ratio of hard and soft segments (PDMS:MDI:ED = 1:2:1; 20 wt. % of the hard segments) were synthesized in two different solvent mixtures, by a two-step polyaddition procedure. The first one was tetrahydrofuran/N,N-dimethylacetamide (THF/DMAc) with different co-solvent ratios (1/1, 1/2 and 1/9, v/v), whereas the second one was tetrahydrofuran/N-methylpyrrolidone (THF/NMP, 1/9, v/v). The reaction conditions were optimized by varying the co-solvents ratio, the concentration of the catalyst, the initial monomer concentration, as well as the time of the first and the second step of the reaction. The effects of the experimental conditions on the size of the PUUS were investigated by gel permeation chromatography (GPC) and dilute solution viscometry. The copolymers with the highest molecular weights were obtained in the THF/NMP mixture (1/9, v/v). The structure and composition of the copolymers were determined by 1H-NMR and FTIR spectroscopy. The morphology of the synthesized copolymers was investigated by atomic force microscopy (AFM), while the thermal properties were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The surface properties were evaluated by measuring the water contact angle (WCA). The copolymers exhibited phase-separated microstructure and were stable up to 200°C in nitrogen.

Segmentirani poli(uretan-urea-siloksani) (PUUS), sa tvrdim segmentima na bazi 4,4'-metilendifenildiizocijanata i etilendiamina (MDI-ED) i mekim segmentima na bazi hidroksipropil-terminiranog poli(dimetilsiloksana) (PDMS, Mn = 1000 g mol-1), sintetisani su pod različitim eksperimentalnim uslovima. Kopolimeri sa konstantnim molskim odnosom tvrdih i mekih segmenata (PDMS:MDI:ED = 1:2:1; 20 mas. % tvrdih segmenata), sintetisani su u dve različite smeše rastvarača kao reakcionog medijuma, metodom dvostepene poliadicije. Prva kombinacija rastvarača je bila smeša tetrahidrofurana (THF) i N,N-dimetilacetamida (DMAc), dok je u drugom slučaju korišćena smeša THF-a i N-metilpirolidona (NMP). Reakcioni uslovi su optimizovani u pogledu odnosa ko-rastvarača, koncentracije katalizatora, početne koncentracije monomera i vremena odigravanja prve i druge faze reakcije. Ispitan je uticaj primenjenih eksperimentalnih uslova na veličinu PUUS primenom gel-propusne hromatografije (GPC) i viskozimetrije razblaženih rastvora [η]. Kopolimeri najvećih molarnih masa su dobijeni u smeši THF/NMP (1/9, v/v). Struktura i sastav kopolimera su okarakterisani 1H-NMR i FTIR spektroskopijom. Morfologija sintetisanih kopolimera je ispitana mikroskopijom atomskih sila (AFM), dok su termička svojstva ispitana diferencijalnom skenirajućom kalorimetrijom (DSC) i termogravimetrijskom analizom (TGA). Površinska svojstva kopolimera su ispitana određivanjem kontaktnih uglova sa vodom (WCA). Kopolimeri su pokazali dvofaznu mikrostrukturu i bili su stabilni do 200°C u atmosteri azota.