Telechelic Poly(methyl acrylate)s as Constituents for Multiblock Poly(urethane urea)s

New poly(urethane urea)s based on telechelic poly(methyl acrylate)s (PMAs) and different diisocyanates and diamines are prepared by a two‐step polyaddition process—formation of an isocyanate telechelic prepolymer followed by chain extension with a diamine to form the final poly(urethane urea)s. Hydroxyl‐telechelic or mixed amino‐hydroxyl‐telechelic PMAs are obtained by two different concepts: (i) according to the first concept methyl acrylate (MA) was polymerized by single electron transfer‐living radical polymerization (SET‐LRP) using 2‐hydroxyethyl 2‐bromoisobutyrate as initiator followed by nucleophilic substitution of the halogen end group with n‐butylamine, 2‐methylamino ethanol, or 3‐amino‐1‐propanol and (ii) according to the second concept after SET‐LRP under the same conditions the halogen end group is converted to an azide followed by a click reaction using sodium azide and propargyl alcohol in a one‐pot reaction. Applying the second concept, a hydroxyl‐functional PMA with a share of 83 mol% bifunctionality is obtained. This PMA‐diol is used in polyaddition reaction with different diisocyanates (isophorone diisocyanate (IPDI), 4,4′‐methylenebis(cyclohexyl isocyanate) (HMDI), and 4,4′‐methylenediphenyl diisocyanate (MDI)) resulting in an isocyanate‐telechelic prepolymer followed by chain extension with the corresponding diamines (isophorone diamine (IPDA), 4,4′‐methylenebis(cyclohexyl amine) (HMDA), and 4,4′‐methylenediphenyl diamine (MDA)). The polyurethane based on hydroxyl‐telechelic PMAs and IPDI/IPDA has a molecular weight of M_n = 44 500 g mol^?1 and a dispersity ? = 3.5, respectively; those based on HMDI/HMDA and MDI/MDA have M_n = 24 600 g mol^?1 and ? = 2.2 and M_n = 16 100 g mol^?1 and ? = 2.0, respectively.

     

Poly(vinylsaccharide)s, 2 Synthesis of some poly(vinylsaccharide)s of the amide type and investigation of their solution properties

The structure and synthesis of some poly(vinylsaccharide)s is described. Five different monomers, N-saccharide-substituted acryl-and methacrylamides, were prepared and polymerized to high molecular weight products using different initiator systems. The influence of the chemical structure of the saccharide moiety on the solution properties was studied by viscosity and light scattering measurements, and a comparative discussion of the solution behaviour of poly(2-deoxy-2-methacrylamido-D-glucose), poly(1-deoxy-1-methacrylamido-D-glucitol), poly(1-acrylamido-1-deoxy-D-glucitol) and polyacrylamide is made. The effects of hydrogenation on the intrinsic viscosity of poly(2-deoxy-2-methacrylamido-D-glucose) is shown. The crosslinking of poly(1-acrylamido-1-deoxy-D-glucitol) as a side reaction was examined by ¹³C NMR spectroscopy.     

Stereoregularity of polystyrene derivatives, 2. Poly(methoxystyrene)s Obtained by Anionic Catalysts.

The stereoregularity of poly(methoxystyrene)s was determined from the absorption of the aromatic C¹ carbon assuming a first-order Markov statistics holds for the polymerization as well as polystyrenes. The stereoregularity of poly(p-methoxystyrene)s prepared by sodium, potassium, or rubidium cations as catalysts in THF hardly varied and syndiotactic-rich polymers were obtained, whereas a random polymer was formed with cesium-naphthalene. In the polymerization of p-methoxystyrene in toluene, syndiotactic-rich polymers were obtained with butyllithium and random polymers were prepared by sodium or potassium cations as catalysts. The stereoregularity of poly(o-methoxystyrene)s prepared by sodium or potassium cations in tetrahydrofuran changed with the polymerization temperatures, and highly syndiotactic polymers were formed at?78°C. The structure of poly(o-methoxystyrene)s obtained in toluene, markedly depended on the initiators; that is, with increasing the size of the ionic radius of the counterions, the isotacticity of the polymers decreased. The mechanism of the polymerization and the substituent effect of the stereoregularity are discussed.     

Photolysis of poly(methyl acrylate) in solution

Solutions of poly(methyl acrylate) in methyl acetate, chloroform, methylene dichloride and benzene have been irradiated by 2 537 Å radiation and changes in number average molecular weight measured. The effect of time of irradiation, solvent, polymer concentration and the presence of radical initiator have been investigated and it is concluded that the scission results from random absorption of radiation directly by the polymer without direct participation by the solvent which acts only as an optical filter.     

Macroporous poly(sucrose acrylate) hydrogel for controlled release of macromolecules

We have studied the controlled release of proteins from poly(sucrose acrylate) hydrogels. The hydrogels were prepared by a two-step procedure in which sucrose was first acylated to sucrose-1′-acrylate followed by free radical polymerization. By adjusting the cross-link ratio and initial monomer concentration, the swelling ratio of the hydrogel was varied from five to 28. The mechanical strength of these hydrogels was comparable to that of other hydrogels with approximately the same swelling ratio. Scanning electron micrographs and mesh size calculations indicate that the hydrogel is macroporous, suggesting it may be suitable for a variety of biomedical applications. The release kinetics of β-lactoglobulin, bovine serum albumin and γ-globulin were studied as a function of initial monomer concentrations for the sucrose-based hydrogel. All of the release profiles were characterized by an initial burst of protein in the first 25 h followed by a long period of sustained release (s> 500 h). The magnitude of the initial burst was reduced by increasing the initial monomer concentration and by increasing the molecular weight of the protein. A quantitative model based on the heterogeneous nature of the hydrogel was developed to explain the observed release kinetics.     

The reaction of propane sultone with macromolecules. III. Poly(ethylene imine)

The reaction of propane sultone with poly(ethylene imine) (PEI) has been studied in benzene and in methanol. The reaction products are polyampholytes insoluble in water or any other solvent, but soluble in strong alkali or in concentrated acids. Depending on the molar ratio PEI: propane sultone, products having a degree of substitution between 0.23 and 0.64 were obtained. After treatment with excess sodium hydroxide and removal of the excess by dialysis, a polymer containing both sodium sulfopropyl groups and sulfopropyl groups in form of inner ammonium salts was obtained.     

The reaction of propane sultone with macromolecules. II. Poly(vinyl alcohol)

The sulfopropylation of poly(vinyl alcohol) (PVA) with propane sultone under different conditions has been studied. Attempts to carry out the reaction via the sodium alcoholate of PVA, prepared by different methods, failed, gave low yields or resulted in the formation of insoluble reaction products. The best way to obtain sulfopropyl poly(vinyl alcohol) (SPPVA) was to react propane sultone with PVA dissolved in dimethyl sulfoxide (DMSO) in the presence of potassium carbonate. Most probably the reaction occurs via dimethyl-(3-sulfopropoxy)sulfonium salt which is formed by reaction of propane sultone with DMSO. By passing a solution of the potassium salt of SPPVA through an acidified ion exchange column the free acid was obtained. Both the potassium salts and the free acids were hygroscopic, water-soluble substances showing typical polyelectrolyte properties.     

Investigation of Chain Dynamics in Poly(n‐alkyl methacrylate)s by Solid‐State NMR: Comparison with Poly(n‐alkyl acrylate)s

PnAMAs exhibit a local nanophase separation associated with intriguing chain dynamics (Macromol. Chem. Phys. 2005 , 206, 142). PnAMAs of high molar mass, as determined by SEC and MHKS parameters, were investigated in the melt with a recently‐developed solid‐state NMR method (NOE with dipolar filter; Solid State Nucl. Magn. Res. 2005 , 28, 160). The correlation times are assigned to the relaxation of the alkyl nanodomains, as coupled motions of the main chain and hindered local modes in the side chain. Comparison with poly(n‐alkyl acrylates) shows a higher anisotropy of the main chain motions and a better organized local nanophase separation in PnAMAs.

     

Degradation of Poly(butyl acrylate) and Poly(2‐hydroxyethyl methacrylate) Model Compounds Under Extreme Environmental Conditions

The degradation of low‐MW ( = 1 500 g · mol^?1) model compounds of pBA and pHEMA were studied under conditions corresponding to the worst‐case temperatures and irradiation intensities likely to be experienced by a surface coating exposed to the harsh Australian environment. Vinyl‐terminated polymers were compared to their saturated analogues; the terminal vinyl bond was found to be a source of instability which rendered the polymers more susceptible to degradation. The cyclic degradation mechanism derived from degradation of pMMA in our previous publication is also relevant to pBA and pHEMA. In addition, pBA and pHEMA are susceptible to other degradation and crosslinking reactions; crosslinking is particularly rapid in pHEMA exposed to UV radiation.

     

Poly(urethane-parabanic acid)s

Oligoureas with diisocyanato end groups (6a – f) were transformed into the respective parabanic acid derivatives (7a – f) with the aid of oxalyl chloride (2) . In the reaction of 2 with certain diurea model compounds (12) in 1,2-dichloroethane at room temperature besides the corresponding parabanic acids, diurea dihydrochlorides were formed. Their solutions in 1,2-dichloroethane exhibit electrical conductivity. IR spectra confirm their structure. The reaction of the α,ω-diisocyanatopoly(parabanic acid)s with diols (8a – e) led to copolymers and block copolymers, poly(urethane-parabenic acid)s. The experimental conditions and the influence of the structure of the polymers on certain properties of the final products were investigated.     

Water Structure and Blood Compatibility of Poly(tetrahydrofurfuryl acrylate)

We previously reported that poly(2-methoxyethyl acrylate) (PMEA), which has excellent blood compatibility, contains a large amount of freezing bound water. In order to confirm the role of freezing bound water in determining blood compatibility, poly(tetrahydrofurfuryl acrylate) (PTHFA) was newly synthesized and the thermal properties of water in PTHFA were investigated by differential scanning calorimetry (DSC), as freezing bound water was observed as cold crystallization in DSC heating curves. In addition, the blood compatibility of PTHFA, including activations of platelets, the coagulation system and the complement system, was investigated. The temperature of cold crystallization of water in PTHFA was higher than that of water in PMEA; moreover, the amount of freezing bound water in PTHFA was smaller than that in PMEA. The effect of freezing bound water on blood compatibility was investigated by comparing PTHFA, PMEA, poly(2-hydroxyethyl methacrylate) (PHEMA) and poly(2-methoxyethyl methacrylate) (PMEMA). The latter two samples showed no cold crystallization. Activations of platelets, the coagulation system and the complement system were enhanced in the following order: PMEA < PHEMA < PTHFA < PMEMA, PMEA < PMEMA < PTHFA < PHEMA and PMEA < PTHFA < PMEMA < PHEMA, respectively. The above results were reasonably explained by the amount and/or the stability of freezing bound water.     

Poly(oxyethylene)s terminated at both ends with phosphonium ion end groups, 2. Properties

Poly(oxyethylene)s with number-average degrees of polymerization (DP_n) ranging from ≈ 6 to ≈ 80, terminated at both ends with phosphonium ion end groups (diionic poly-EO), have been prepared and characterized as described in the preceding paper. Viscosities of diionic poly-EO were measured, both in solution and in bulk. In chloroform solution, at low concentration (< 1 g/100 mL), the viscosity of diionic poly-EO was lower than the viscosity of nonionic (terminated with HO-groups) poly-EO of the same DP_n. At higher concentrations, the viscosity of diionic poly-EO exceeded that of nonionic poly-EO and increased sharply with increasing concentration. At the constant weight concentration of ≈4 g/100 mL, the viscosities of short-chain diionic poly-EO were higher and those of longer chain diionic poly-EO were lower than the viscosities of the nonionic poly-EO of the same chain lengths. These results were attributed to a predominant intramolecular aggregation of terminal ionic groups at low concentration of ionic groups in solution and predominant intermolecular aggregation at higher concentration of ionic groups. The results of bulk viscosity measurements as well as the results of differential scanning calorimetry measurements of the dependence of the glass transition temperature on the DP_n of diionic poly-EO indicated that in bulk physically cross-linked networks were formed, due to intermolecular aggregation of terminal ionic groups.     

Preparation of poly(amide-imide)s by direct polycondensation with triphenyl phosphite, 3. Poly(amide-imide)s based on bis(trimellitimide)s

Six dicarboxylic acids ( 1a–f ) were prepared from trimellitic anhydride and 4,4′-oxydianiline, 4,4′-methylenedianiline, 4,4′-sulfonyldianiline, benzidine, 1,6-hexamethylenediamine, and 4,4′-methylenedicyclohexylamine. These diacids were condensed directly with various aromatic diamines using triphenyl phosphite in 1-methyl-2-pyrrolidone/pyridine solution in the presence of calcium chloride. The inherent viscosity of the polymers is affected by the nature of the diamine and the solubility of the resulting polymers in the reaction media. The highest η_inh-value of a poly(amide-imide) obtained was 1,41 dl/g (in N,N-dimethylacetamide/5% LiCl at 30°C). Among the polymers, the wholly aromatic ones show better solubility, higher glass transition temperatures, and higher thermostability than the aliphatic-aromatic ones. Well-defined melting points (T_m) of most wholly aromatic poly(amide-imide)s were not obtained by differential scanning calorimetry (DSC); however, some poly(amide-imide)s containing aliphatic chains showed clear T_m in the first DSC heating traces. Measurements of wide-angle X-ray diffraction revealed that those polymers containing biphenyl or linear hexamethylene groups are partially crystalline. Flexible films with excellent tensile properties were cast from N,N-dimethylacetamide solutions of most of the wholly aromatic poly(amide-imide)s.     

Poly(vinylsaccharide)s, 4. Synthesis and polymerization of 6-o-methylallylgalactose derivatives

Methylallyl ethers of 1,2:3,4-di-O-isopropylidene-D-galactopyranose and 1,2:3,4-di-O-cyclohexylidene-D-galactopyranose were synthesized as new monomers containing saccharide moieties and copolymerized with maleic anhydride. The hitherto unknown 6-O-(2-alkoxycarbonylallyl)-1,2:3,4-di-O-isopropylidene-D-galactopyranoses ( 8a and 8b; alkyl: methyl and ethyl, respectively) were prepared and polymerized under free radical conditions. The substances were characterized by ¹³C NMR, elemental analyses and molecular weight determinations. Water solubility of these polymers was obtained by removing the isopropylidene protecting groups. The inherent viscosities of these polymers, measured in 0,1 M Na₂SO₄ aqueous solution, were of the same order of magnitude as those of polyacrylamides of the corresponding degrees of polymerization.     

Interaction between polynucleotides in aqueous NaCl solution, 4. Poly(riboadenylic acid) — poly(2-riboinosinic acid) system

Solution properties of poly(A) and poly(I) solution at a mole ratio of poly(A) to poly(I) of 1/2 were studied by means of calorimetry and a modified differential scanning calorimetry (DSC) with the help of circular dichroism (CD) and ultraviolet (UV) spectral methods. It was found that the heat of mixing, ΔH^M, depends sharply on the ionic strength. At [NaCl] < 10^?2 mol · dm^?3 ΔH^M is nearly zero. At higher ionic strength ΔH^M decreases and reaches a minimum value at [NaCl] ≈? 2 · 10^?2 mol ? dm^?3. Above this ionic strength ΔH^M increases again. This behavior is explained on the basis of the formation of a triplex poly(A) · poly(2I) and the transition of poly(I) from a disordered to an ordered structure with increasing ionic strength. The heat of formation, ΔH, of the poly(A) · poly(21) triplex was estimated to be ca ?41 kJ per mole of base triplet. Above an NaCl concentration of 2 · 10^?1 mol · dm^?3 the triplex formation may be represented by the following scheme:      

Chain and Step Growth Polymerizations of Cyclic Imino Ethers: From Poly(2‐oxazoline)s to Poly(ester amide)s

Cyclic imino ethers (CIEs), such as 2‐oxazolines and 2‐oxazines are a unique class of monomers, which because of their manifold reactivities can be polymerized via multiple techniques. Most prominent, the living cationic ring‐opening polymerization (CROP) of CIEs enables the synthesis of well‐defined tailor‐made poly(CIEs), which have tremendous importance as functional and biocompatible polymers. On the other hand, CIEs are also powerful monomers in polyadditions resulting in the formation of a variety of biodegradable polyamide‐based systems. In this contribution, the enormous potential of CIEs as functional building blocks is discussed, which goes well beyond the CROP. Besides trends in the CROP of CIEs, recent developments in step‐growth polymerizations of CIEs are highlighted, including the spontaneous zwitterionic copolymerization (SZWIP) which provides access to functional alternating N‐acylated poly(amino ester)s (NPAEs) and polyadditions of multifunctional CIEs which give main‐chain poly(ester amide)s (PEAs).

     

MALDI‐TOF Analysis of Halogen Telechelic Poly(methyl methacrylate)s and Poly(methyl acrylate)s Prepared by Atom Transfer Radical Polymerization (ATRP) or Single Electron Transfer‐Living Radical Polymerization (SET‐LRP)

Poly(methyl methacrylate)s (PMMA)s and poly(methyl acrylate)s (PMA)s are prepared by atom transfer radical polymerization (ATRP) or single electron transfer‐living radical polymerization (SET‐LRP) using methyl dichloroacetate (MDCA) and ethyl dibromoacetate (EDBA) as bifunctional initiators. The chain‐end functionality is determined by MALDI‐TOF mass spectrometry. The target PMMA (M_n = 2000 g mol^?1) and PMA (M_n = 2000 g mol^?1) samples obtained by ATRP of MMA and MA with MDCA as initiator have 12 and 81 mol% bis‐chloro end groups, respectively; those prepared by SET‐LRP have 57 and 100 mol% bis‐chloro end groups, respectively. The PMMAs obtained by ATRP or SET‐LRP with EDBA have no bromine end groups.

     

Facile Preparation of Monodisperse Poly(2‐hydroxyethyl acrylate)‐Grafted Poly(methyl methacrylate) Microspheres via Photoinitiated RAFT Dispersion Polymerization

Highly monodisperse poly(2‐hydroxyethyl acrylate)‐grafted poly(methyl methacrylate) (PMMA) microspheres are prepared by a facile photoinitiated dispersion polymerization in ethanol/water mixtures at room temperature. Poly(2‐hydroxyethyl acrylate) homopolymers with different molecular weights are synthesized via reversible addition‐fragmentation chain transfer (RAFT) solution polymerization and employed as steric stabilizers in photoinitiated dispersion polymerization. The effect of macro‐RAFT agent (both concentration and molecular weight) on particle diameter is studied in detail. Kinetic study indicates that the polymerization proceeded rapidly with 96% yield being reached with 1 h of UV irradiation. Finally, the obtained hydroxyl‐rich PMMA microspheres are used as building blocks for the preparation of covalently cross‐linked colloidosomes.

     

Stereoregularity of polystyrene derivatives, 3. Poly(methylstyrene)s Obtained by Anionic Catalysts

The stereoregularity of the polymers of ortho-, meta-, and para-methylstyrenes prepared with various anionic catalysts was determined by means of ¹³C NMR spectroscopy. The substituent effect on the stereoregularity was discussed comparing with that of polystyrenes obtained under the same polymerization conditions. Syndiotactic-rich poly(methylstyrene)s were prepared with butyllithium in toluene and the syndiotacticity increased in the order of para-, meta-, and ortho-derivatives. Although the structure of the polymers prepared with sodium-naphthalene (Na-naph.) in THF did not change with the position of the substituent, in toluene, however, the methyl group at ortho-position influences the stereoregularity. The trend of the stereoregularity of the polymers produced by potassium-naphthalene was almost the same as that of poly(methylstyrene)s prepared by Na-naph. Nearly random polymers were obtained with the cesium ion as catalyst.