Poly Ether Urethane Ureas Research Articles

Polyether Urethane Ureas with Heterogeneous Rigid Blocks

An investigation was made of the structure and properties of segmented polyether urethane ureas with heterogeneous rigid blocks, obtained using 2,4-toluylene diisocyanate and isophorone diisocyanate. Extremal dependences of the physicomechanical and thermal characteristics of the materials on the composition of the rigid blocks were found. The relationship between the structure and properties of the new type of block copolymer was established.

Study of the relationship between crack tip strain and crack propagation in polyurethane films using micro- FTi.r.

In the present study, a series of polyether-urethane-ureas (PEUU) were selected for investigation of crack propagation behaviour under dynamic loading conditions. These model polyurethanes were synthesized by two-stage polymerization. The hard segments were composed of 4,4′-diphenyl methane diisocyanate (MDI) and ethylene diamine (EDA). The soft segments were polyglycols having different chemical structures and number average molecular weights of 1000 and 2000. Monitoring of the variation in molecular orientation at the crack tip region was accomplished using polarized FTi.r. microscopy. Molecular orientation of the four major functional groups, NH, CH-, C=O, and C=C representing the domain, matrix, and interface region were measured as a function of strain for uncracked samples using the i.r.-dichroism technique. NH- and C=O functional groups present in the urea and correlated with the hard domains behaviour, exhibit a generalized orientation function-strain curve which was characterized by three regions. Region 1 was associated with an initial decrease in the orientation function at low strains followed by region 2, which is the minimum obtainable orientation, and region 3 a subsequent increase in the orientation function with an increase in strain. The molecular orientation was used to determine the real strain at the crack tip. The strains at the crack tip for the pure (PEUU) were between 4 to 7 times higher than the applied strain. It was observed that higher soft segment molecular weights correlated with a larger strain at the crack tip. For the same soft segment molecular weights, polypropylene glycol (PPG) based PEUU showed higher strains at the crack tip. Therefore, the strain at the crack tip depends on chemical structure and the molecular weight of the soft segment. According to the strain data and the generally accepted deformation theory for PEUU elastomers, in all PEUUs, crack propagation occurred after the individual hard segments separated and oriented along the stretching direction.

Preparation and Characterization of Polyetherurethaneureas Containing Methyl- or Fluoro Substituted Biphenyldiyl in Hard Segments.

メチルあるいはフッ素置換ビフェニル-4,4'-ジオール(BP,nMBP,nFBP)を含むポリエーテルウレタソ尿素(PEUUs)をポリテトラヒドロフラソff1000(PTHF),4 ,4'-メチレンビス(フェニルイソシアナート)(MPI),および鎖延長剤にエチレソジアミン(EDA)を用いる典型的な2段階重付加重合法から得た.ここに,置換ビフェニルジオールは4,4'-biphenyldio1(BP) ,3,3'-dimethy1-4,4'-bipheny1-diol(2MBP),3,3',5,5'-tetramethy1-4,4'-biphenyldio1(4MBP),3,3'-difluoro-4,4'-biphenyldiol(2FBP)および3,3,5,5'-,tetrafluoro-4,4'-biphenyldio1(4FBP),2,2',3,3' ,5,5',6,6'-octafiuoro-4,4'-bipheny1-dio1(8FBP)である.仕込みモル比をPTHF:置換ビフェニルジオール:MPI:EDA=O .5:0.5:2:1とし,DMSO:IBMK(1:1)の混合溶媒中で反応させてそれぞれPEUUs(PEUU-BP,PEUU-nMBPおよびPEUU-nFBP)を得た.また,ビフェニルジオール誘導体を含まないPEUUもPTHF:MPI:EDA=1:2:1のモル比で合成した.XPS測定から,空気中ではビフェニルジオール部を含む疎水性セグメントが表面付近に配向していることがわかった.水に対する接触角(θ)から,ビフェこルジイルにメチル基あるいはフッ素を導入するとPEUU表面の疎水性が向上することを確認した.PEUU_4MBPおよびPEUU-4FBPフィルムの引張り弾性率(E)はそれぞれ109 .1MPaおよび129.3MPaであった.また,PEUU-nMBPおよびPEUU-nFBPはいずれもウシ血清アルブミソおよびヒト血清γ-グロブリンを単層で吸着することを見い出した.細胞接着試験から,PEUUフィルムはマウス繊維芽細胞(L-929)の接着性を示した.これらの力学的性質および生体適合性から,PEUU-nMBPとPEUU-nFBPは人工血管として有用な材料となることが期待される.

Photostability of polyetherurethaneureas

AbstractPolyetherurethaneureas (PEUUs) were synthesised from polyethylene‐glycols (PEGs) of molecular weight 400, 600 and 1000, 4,4′‐diphenylmethanediisocyanate (MDI) and aliphatic diamine chain extenders, 1,3‐propanediamine (PDA) and 1,6‐hexanediamine (HDA). Polymer films were irradiated with 365 nm light at 293 K and the effects of polyether soft segment length and urea hard segment on photo‐oxidative stability were studied by following the variation in weight‐average molecular weight (Mw), gel formation and stress‐strain properties. Changes in ultraviolet and infrared spectroscopy were monitored on photo‐oxidation and hydroperoxide content determined. The soft segment length was increased by increasing the molecular weight of PEG from 400 to 1000 and hard segment structure was changed by variation of diamine. It was noted that the structure of urea and polyether soft segment length plays an important role in photostability of PEUUs. PDA chain extended PEUUs were more stable than HDA chain extended PEUUs.

Correlation between the microstructure and properties of haemocompatible polyetherurethane ureas

The effect of the proportion of rigid blocks in segmented polyetherurethane ureas on their mechanical properties is studied. It is established that there are two critical points on the plots of the properties of the polymers against temperature, in which the nature of the behaviour of the system changes its character. It is shown by small angle X-ray scattering that at these points the type of supermolecular (domain) structure of the polyetherurethane urea changes.

Heat capacity of crown-containing polyetherurethane ureas

The heat capacity of polyethereruthane ureas initial and hardened from the melt and containing macrocyclic polyester dibenzo-18-crown-6 in the backbone has been investigated by DSC in the interval 140–470 K. Analysis of the results in terms of the Couchman equation showed that the nature of the flexible segment, its MM and the thermal prehistory of the sample significantly influence the process of microsegregation in the polymers studied and manifestation of conformational rearrangements in the crown ether fragments of the macrochain.

A birefringence study of molecular and supermolecular structure in polyether urethane-ureas

Polyether urethane-ureas with alternating flexible and stiff-chain segments were studied by static and time-dependent birefringence. Four temperature regions characterized by different molecular mobility have been identified. The hard segments are assumed to be segregated to form domains embedded in a matrix of the soft, polyether segments. The stiff-chain segments inside the domains are oriented perpendicularly to the largest domain dimension. The length of the statistical segment in the stiff-chain blocks is A ⩾ 13 nm.

Attachment and proliferation of fibroblast cells on polyetherurethane urea derivatives

Interactions of novel polyetherurethane urea derivatives with fibroblast cells as well as with plasma proteins were investigated. Fibronectin, which is a cell adhesion protein, was found to be very active in attaching fibroblast cells onto a heparinized polyetherurethane urea: its activity was found to be strongly dependent on the surface properties of the material. Fibronectin was easily adsorbed by the heparinized polyetherurethane urea, but the degree of its adsorption to the material in competition with other proteins was so low that cell attachment to polyetherurethane ureas was decreased by heparinization. Different degrees of cell attachment onto different materials due to different adsorptivities of plasma proteins were considered. Proliferation of fibroblast cells was suppressed on cationic polyetherurethane urea but unaffected on other derivatives of polyetherurethane urea. Since specific suppression of cell proliferation was not observed on the heparinized polyetherurethane urea, the latter material was expected to be useful as a long-term antithrombogenic material in vivo.