Calcium‐containing poly(urethane‐urea)s: Synthesis,spectral, and thermal studies

A calcium salt of mono(hydroxypentyl)phthalate [Ca(HPP)₂] was synthesized by the reaction of 1,5‐pentanediol, phthalic anhydride, and calcium acetate. Four different bisureas such as hexamethylene bis(ω,N‐hydroxyethylurea), tolylene 2,4‐bis(ω,N‐hydroxyethylurea), hexamethylene bis(ω,N‐hydroxypropylurea), and tolylene 2,4‐bis(ω,N‐hydroxypropylurea) were prepared by reacting ethanolamine or propanolamine with hexamethylene diisocyanate (HMDI) or tolylene 2,4‐diisocyanate (TDI). Calcium‐containing poly(urethane‐urea)s (PUUs) were synthesized by reacting HMDI or TDI with 1:1 mixtures of Ca(HPP)₂ and each of the bisureas with di‐n‐butyltin dilaurate as a catalyst. The PUUs were well characterized by Fourier transform infrared spectroscopy, ¹H and ¹³C NMR, solid‐state ¹³C–cross‐polarization/magic‐angle spinning NMR, viscosity, solubility, elemental analysis, and X‐ray diffraction studies. Thermal properties of the polymers were also examined with thermogravimetric analyses and differential scanning calorimetry. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1809–1819, 2004     

Synthesis of poly(urethane urea) by in situ polymerization inside stone

The first synthesis of poly(urethane urea) by in situ polymerization inside stone was successfully carried out. Poly(propylene glycol), isophorondiisocyanate, and a catalyst [tin(II) ethyl hexanoate, aluminum acetylacetonate, or zirconium acetylacetonate] were mixed with acetone in petri dishes, and tuff samples were placed in the dishes at room temperature. The effects of the comonomer ratio, catalyst, and catalyst concentration on the chemical structure of the synthesized poly(urethane urea) were investigated. The poly(urethane urea) distribution inside the tuff and the related morphology were also analyzed, as well as the reversibility of the performed treatments. Finally, the effects of the in situ polymerization polymer on the properties of the stone, such as water capillary absorption and permeability to water vapor, were assessed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 542–552, 2005     

Solvent‐free and nonisocyanate melt transurethane reaction for aliphatic polyurethanes and mechanistic aspects

A novel melt transurethane polycondensation route for polyurethanes under solvent‐free and nonisocyanate condition was developed for soluble and thermally stable aliphatic or aromatic polyurethanes. The new transurethane process was investigated for A + B, A‐A + B, and A‐A + B‐B (A‐urethane and B‐hydroxyl) ‐type condensation reactions, and also monomers bearing primary and secondary urethane or hydroxyl functionalities. The transurethane process was confirmed by ¹H and ¹³C NMR, and molecular weight of the polymers were obtained as M_n = 10–15 × 10³ and M_w = 15–45 × 10³ g/mol. The mechanistic aspects of the melt transurethane process and role of the catalyst were investigated using model reactions, ¹H NMR, and MALDI‐TOF‐MS. The model reactions indicated the occurrence of 97% reaction in the presence of catalyst, whereas its absence gave only less than 2% of the product. The polymer samples were subjected for end‐group analysis using MALDI‐TOF‐MS, which confirms the Ti‐catalyst mediated nonisocyanate pathway in the melt transurethane process. Almost all the polyurethanes were stable up to 280 °C, and the T_g of the polyurethanes can be easily fine‐tuned from ?30 to 120 °C by using appropriate diols in the melt transurethane process. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2445–2458, 2008     

Effect of side groups of polymer glycol on microphase‐separated structure and mechanical properties of polyurethane elastomers

The effect of side methyl and dimethyl groups of the soft segment component on the microphase‐separated structure and mechanical properties of polyurethane elastomers (PUEs) was investigated. Poly(oxytetramethylene) glycol (PTMG), and PTMG incorporating dimethyl groups (PTG‐X) and methyl side groups (PTG‐L) were used as a polymer glycol, which forms a soft segment in the PUEs. The PUEs were synthesized with 4,4′‐dipheylmethane diisocyanate [1,1′‐methylenebis(4‐isocyanatobenzene)], 1,4‐butane diol, and 1,1,1‐trimethylol propane by a prepolymer method. The degree of microphase separation of the PUEs became weaker with increasing side group content in polymer glycols. Dynamic viscoelastic properties measurement showed reorganized‐crystallization and melting of the soft segment for the PUEs based on PTMG, PTG‐L, and PTG‐X with a lower content of the side groups, but not for a PTG‐L and PTG‐X with higher content of the side groups. Tensile testing revealed that increasing methyl group concentration made the PUEs soften and weaken. The PTMG‐based PUEs obviously exhibited strain‐induced crystallization of the soft segment chains during elongation process. In contrast, for the PTG‐L and PTG‐X‐based PUEs, crystallinity decreased with increasing side group content, and the PUEs with PTG‐L and PTG‐X with highest methyl group content did not crystallize even at a large strain. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2054–2063, 2008     

Lysine‐based functional blocked isocyanates for the preparation of polyurethanes provided with pendant side groups

This article describes a methodology to prepare polyurethanes (PUs), decorated with pendant (bio)functional side groups, by polymerizing (bio)functionalized blocked diisocyanates with polyols. Caprolactam blocked lysine diisocyanate methyl ester (BLDI‐OMe) was prepared in high yields, by reacting the methyl ester of lysine with carbonyl biscaprolactam. In the absence of a catalyst, the polymerization of BLDI‐OMe with polycaprolactone and polytetrahydrofuran resulted in strictly linear PUs due to the high selective reactivity of the blocked isocyanates (BIs). Although the ester appeared to be less reactive, we found hydrolyzing conditions for the ester, without affecting the BIs. The free acid groups were converted into a N‐hydroxysuccinimide (NHS) activated ester, which was a versatile intermediate for further functionalization. After having demonstrated that model amines were able to substitute NHS without effecting the BIs groups, the same chemistry was used to couple biotin, giving a biotin functional caprolactam blocked lysine diisocyanate. The polymerization with polyols afforded the corresponding biotin‐functional PUs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2036–2049     

Chemo- and Regioselective Additions of Nucleophiles to Cyclic Carbonates for the Preparation of Self-Blowing Non-Isocyanate Polyurethane Foams

Polyurethane (PU) foams are indisputably daily essential materials found in many applications, notably for comfort (for example, matrasses) or energy saving (for example, thermal insulation). Today, greener routes for their production are intensively searched for to avoid the use of toxic isocyanates. An easily scalable process for the simple construction of self-blown isocyanate-free PU foams by exploiting the organocatalyzed chemo- and regioselective additions of amines and thiols to easily accessible cyclic carbonates is described. These reactions are first validated on model compounds and rationalized by DFT calculations. Various foams are then prepared and characterized in terms of morphology and mechanical properties, and the scope of the process is illustrated by modulating the composition of the reactive formulation. With impressive diversity and accessibility of the main components of the formulations, this new robust and solvent-free process could open avenues for construction of more sustainable PU foams, and offers the first realistic alternative to the traditional isocyanate route.     

Synthetic mimicking of plant oils and comparison with naturally grown products in polyurethane synthesis

The use of plant oils as industrial feedstocks can often be hampered by their lack of optimization towards a particular process, as well as their development being risky; growing suitable volumes of crops to test can take up to five years. To circumvent this, we aimed to discover a method that would mimic plant oil profiles in the laboratory, and show that they exhibited similar properties to the naturally grown plant oils in a given process. Using the synthesis of polyurethanes as an example, we have synthesized six different polymers and demonstrated that plant oils will produce polymers with similar physical properties to those oils mimicked in the laboratory. The use of this mimicking process can be extended to other types of polymers to obtain a method for predicting the properties of a given material based on the plant oil composition of a crop before it is grown in bulk.     

Spectroscopic linear dichroism FT-IR studies of synthetic spider silk

This work deals with the analysis of the orientation behavior of different segments of synthetic spider silk samples containing hard and soft segments. Two different types of spider silk were examined, one with an aliphatic hard segment (hexamethylene-diisocyanate) and an amorphous soft segment (polytetramethylene oxide) (A40) and the other with an aromatic hard segment (4,4′-methylene bisphenyl diisocyanate) and a semicrystalline soft segment (polyethylene oxide-polypropylene oxide- polyethylene oxide) (A143). In order to observe the orientation behavior of the hard and the soft segments it was necessary to define marker bands. While for both samples the chosen marker bands for the hard segments were the same, the marker bands for the soft segments were different. FT-IR spectra were recorded while strain was applied to the material at the same time. Two parameters, the dichroic ratio R and the order Parameter f were used to evaluate the behavior of these materials under conditions of strain. It was found that sample A143 broke at a strain level of 37,5 %, while sample A40 showed a high dynamic range up to a strain level of 307 %.     

Segmented Polyurethanes for Medical Applications: Synthesis,Characterization and in vitro Enzymatic Degradation Studies

Degradable segmented poly(ether-ester-urethanes) of variable segment chemistry and content were synthesized and characterized. Polycaprolactone diol, a series of poly(ether-ester) block copolymers, and a diisocyanate giving non toxic degradation products were used to form the prepolymer. Cyclohexane dimethanol and a L–phenylalanine–based diester (Phe diester) were used as chain extenders. The influence of α-chimotrypsin on the degradation was investigated by exposing the polymers to buffer and enzyme solutions for 12 days. The SEM, SEC, and gravimetric results showed that a significant erosion of the Phe diester containing polymer compared with the control polyurethane occurred in the presence of the enzyme but not in a normal buffer solution.     

Easily grafted polyurethanes with reactive main chain functional groups. Synthesis,characterization, and antithrombogenicity of poly(ethylene glycol)-grafted poly(urethanes)

A novel synthesis of poly(ethylene glycol) (PEG)-grafted poly(urethanes) (PURs) is described based on a precursor PUR containing free amino groups in the main chain. Three different poly(urethane) backbones were prepared: a homopoly(urethane) comprised of N-Bocdiethanolamine (BDA) and 4,4′-methylenebis(phenyl isocyanate) (MDI), a copoly(urethane) (COPUR) consisting of BDA, N-benzyldiethanolamine and MDI, and a poly(urethane urea) (PUU) that was prepared from BDA, MDI, and ethylenediamine as the chain extender. The M_n of these poly(urethanes) ranged from 32,000 to 72,000 g/mol. PEG (750, 1,900, and 5,000 g/mol) was grafted onto the boc-deprotected poly(urethanes) via the chloroformate. Films of the polymers were spin cast from dilute solutions, annealed, and the surfaces analyzed by goniometry. Water contact angle data indicates increasing PEG surface coverage of the poly(urethanes) with increasing PEG molecular weight. Reorientation of the polymer films is evidenced by contact angle hysteresis. Polymer thrombogenicity, which was studied using blood perfusion experiments, shows that COPUR-g-PEG5000 and PUU-g-PEG5000 exhibit very little platelet adhesion. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3441–3448, 1999