Biodegradation Assessment of Poly(Urethane-Dimethylsiloxane)/Organoclay Nanocomposites under Environmental Conditions

The first series of polyurethane network nanocomposites (PUNN) was prepared by in situ polymerization [1,2] from poly(dimethylsiloxane)-based prepolymer as the soft segment and 4,4’-methylene diphenyldiisocyanate and hyperbranched polyester of the third pseudo generation as the hard segment, in the presence of organically modified montmorillonite nanofiller (Cloisite 30B; 0.5 wt.%). The second series of pure polyurethane networks (PUN) without organoclay was also prepared. The composition of prepared materials in both series was varied through variation of soft segment content from 30 to 60 wt.%. Biodegradability of prepared materials was measured using mixed cultures of microorganisms that originated from soil. This test used soil bacteria and fungi to assess the impact of the environment on polymer compounds. This test is intended to determine which polymer compositions are best suited for coating other materials that must endure lengthy exposure to harsh environmental conditions while retaining their principal functionalities. The biodegradation test was performed under aerobic conditions in the dark condition and in a thermostat at 28 °C. Bacterial and fungal mixed cultures were alternated monthly. After 3 and 6 months of the test, the materials were washed with water, dried in a vacuum oven to constant weight, and used for gravimetric measurements of weight loss. The prepared materials before and after biodegradation test were characterized by FTIR spectroscopy. The results showed that pure PUNs (18.35-18.66 wt.% after six months) possess the highest weight loss as compared to PUNNs (from 7.53 to 14.78 wt.% after six months) after incubation of up to six months. PUNN films had lower biodegradation degree as compared the pure PUN films. Biodegradability was lower for materials with lower soft segment content. In FTIR spectra of PUNN after biodegradation differences were noted at approximately 1700-1735 and 3324 cm-1. The structures contributing to strong hydrogen bonds were partially destroyed during the biodegradation process. The results showed that PUNN with 40 wt.% of soft segment (PUNN-40) is the most resistance material to biodegradation. The reason was probably due to more hydrogen bonding between the polymer and Cloisite 30B organoclay and its better mechanical properties of PUNN-40 sample as compared to other prepared PUNN materials. The obtained materials are good candidate as top coating materials exposed to the environmental conditions

Proučavanje morfologije i termomehaničkih svojstava umreženih poli(uretan-siloksana) na bazi hiperrazgranatog poliestra

Two series of polyurethane films based on hyperbranched polyester of the second pseudo-generation (Boltorn®), 4,4'-methylenediphenyl diisocyanate and two different siloxane prepolymers, α,ω-dihydroxy-(ethylene oxide-poly(dimethylsiloxane)-ethylene oxide)(EO-PDMS-EO) and α,ω-dihydroxypropyl-poly(dimethylsiloxane) (HP-PDMS), were prepared by two-step polymerization in solution. The influence of the type and content of soft segment on the morphology, thermomechanical and surface properties of the synthesized polyurethanes was studied by atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), scanning electron microscopy (SEM), dynamic mechanical thermal analysis (DMTA) and water absorption measurements. It was found that these techniques confirmed existence of microphase separated morphology. Synthesized polyurethanes exhibited two glass transition temperatures and one second relaxation process. The results showed that polyurethanes based on HP-PDMS had higher surface roughness, better microphase separation and waterproof performances. Samples synthesized with lower PDMS content had less hydrophobic surface, but higher crosslinking density and better thermomechanical properties.U ovom radu pripremane su dve serije poliuretanskih filmova na bazi hiperrazgranatog poliestra druge pseudo generacije (Boltron), 4,4¢-metilendifenildiizocijanata i dva različita iloksanska pretpolimera kao što su a, ω-dihidroksi- (etilenoksid-poli(dimetilsiloksan)-etilenoksid)(EO-PDMS-EO) i a,ω-dihidroksipro-pilpoli(dimetilsiloksan)(HP-PDMS), dvostepenom polimerizacijom u rastvoru. Uticaj vrste i sadržaja mekog segmenta na morfologiju, termomehanička i površinska svojstva sintetisanih poliuretana je proučavan pomoću mikroskopije atomske sila (AFM), rasipanja X-zraka pod malim uglovima (SAXS), skenirajuće elektronske mikroskopije (SEM), dinamičko mehaničke termičke analize (DMTA) i merenja količine apsorbovane vode. Nađeno je da primenjene tehnike potvrđuju postojanje morfologije mikrofaznog razdvajanja. Sintetisani poliuretani pokazivali su dve temperature ostakljivanja i jedan sekundarni relaksacioni proces. Rezultati su pokazali da poliuretani na bazi HP-PDMS su imali veći koeficijent hrapavosti, bolje mikrofazno razdvajanje i bolju otpornost prema vodi. Uzorci sintetisani sa nižim sadržajem PDMS-a su imali manju hidrofobnost, ali veću gustinu umrežavanja i bolja termomehanička svojstva

Stabilization of aqueous dispersions of poly(methacrylic acid)-coated iron oxide nanoparticles by double hydrophilic block polyelectrolyte poly(ethylene oxide)-block-poly(N-methyl-2-vinylpyridinium iodide)

Aqueous dispersions of poly(methacrylic acid)-coated superparamagnetic iron oxide nanoparticles (PMAA@SPIONs) and nanoparticles obtained by adding a layer of double-hydrophilic cationic block polyelectrolyte poly(ethylene oxide)-block-poly(N-methyl-2-vinylpyridinium iodide) (PEO-QP2VP) on PMAA@SPIONs were studied by a combination of static and dynamic light scattering, SAXS, transmission electron microscopy and atomic force microscopy, probing the structure of the SPION aggregates on the lengthscale from 1 to 10$^3$ nm. Both SALS and AFM results indicate that adding a PEO-QP2VP layer to PMAA@SPIONs decreases the size of SPION aggregates formed in the dispersions. While TEM micrographs show that PEO-QP2VP@PMAA@SPION particles are less apt to form small clusters with the size of several tens nm compared to PMAA@SPION particles, the local clustering has no effect on the power law scattering behavior (I(q) ∼ q$^{−1.4}$) of the SPION dispersions at longer lengthscales (tens to hundreds nm), which reflects mainly polydispersity of the aggregates

Study on the morphology and thermomechanical properties of poly(urethane-siloxane) networks based on hyperbranched polyester

Two series of polyurethane films based on hyperbranched polyester of the second pseudogeneration (Boltorn®), 4,4'-methylenediphenyl diisocyanate and two different siloxane prepolymers, α,ω-dihydroxy-(ethylene oxide-poly(dimethylsiloxane)-ethylene oxide) (EO-PDMS-EO) and α,ω-dihydroxypropyl-poly(dimethylsiloxane) (HP-PDMS), were prepared by two-step polymerization in solution. The influence of the type and content of soft segment on the morphology, thermomechanical and surface properties of the synthesized polyurethanes was studied by atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), scanning electron microscopy (SEM), dynamic mechanical thermal analysis (DMTA) and water absorption measurements. It was found that these techniques confirmed existence of microphase separated morphology. Synthesized polyurethanes exhibited two glass transition temperatures and one second relaxation process. The results showed that polyurethanes based on HP-PDMS had higher surface roughness, better microphase separation and waterproof performances. Samples synthesized with lower PDMS content had less hydrophobic surface, but higher crosslinking density and better thermomechanical properties. (Projekat Ministarstva nauke Republike Srbije, br. 172062