Semiflexible Poly Research Articles

Molecular weight-dependent physisorption of non-charged poly(9,9-dioctylfluorene) onto the neutral surface of cuboidal γ-alumina in toluene

To understand how polymers physisorb onto solid surfaces, we investigated the physisorption behavior of non-charged, semiflexible poly(9,9-dioctylfluorene) (PF8) with three different number-average degrees of polymerization (DPn) as photoluminescent and chromophoric probes onto cuboidal γ-alumina in toluene at 5, 25, and 50 °C. PF8 revealed noticeable DPn and temperature dependencies in its physisorption behaviors. Molecular mechanics (MM)/molecular dynamics (MD) simulations [consistent valence force field (CVFF)] and Moller–Plesset second-order perturbation theory (MP2) with 6-31 G(d,p) calculations suggested that the PF8 in toluene has multiple interactions from CH/π to C–H/O interactions on the (110) surface of γ-alumina. The competition between multiple intermolecular CH/π and C–H/O interactions was crucial for the spontaneous physisorption of PF8 to occur in the presence of a solvent quantity of toluene. Calculations by time-dependent density functional theory (TD-DFT) with Becke three parameter Lee-Yang-Par (B3LYP) method and 6–31 G(d,p) basis set of a model fluorene 9-mer indicated that the π–π* absorption wavelength largely depends on the regularity of the dihedral angles between fluorene rings, while the intensity and spectral width of the π–π* absorption band are largely influenced by the regularity of the dihedral angles. Solution-phase physisorption systems are a result of the inherent nature of several competitive weak intermolecular interactions coexisting among the polymers, surface, and solvents. Noticeable molecular weight and temperature dependency for physisorption behavior of semiflexible, non-charged poly(9,9-n-dioctylfluorene) (PF8) onto cuboidal γ-alumina in toluene were found. MM/MD simulations (CVFF) and quantum mechanical (MP2/6-31G(d,p)) calculations suggested that PF8 swaps interacting toluene for (110) surface of γ-alumina by changing the interaction from CH/π interactions to C-H/O interactions of γ-alumina in toluene. The competition between multiple intermolecular CH/π and C-H/O interactions was crucial whether the spontaneous physisorption of PF8 occurs in place of solvent quantity of toluene. The solution-phase physisorption systems should be the consequence of several weak attractive intermolecular interactions coexisting between polymers, surface, and solvents

A novel strategy for constructing a highly conductive and swelling-resistant semi-flexible aromatic polymer based anion exchange membranes

A novel strategy was proposed to construct a bicontinuous hydrophilic/hydrophobic micro-phase separation structure which is crucial for high hydroxide conductivity and good dimensional stability anion exchange membranes (AEMs). A semi-flexible poly (aryl ether sulfone) containing a flexible aliphatic chain in the polymer backbone with imidazolium cationic group was synthesized by the polycondensation of bis(4-fluorophenyl) sulfone and the self-synthesized 4,4′-[butane-1,4-diylbis(oxy)] diphenol followed by a two-step functionalization. The corresponding membranes were prepared by solution casting. More continuous hydroxide conducting channels were formed in the semi-flexible polymer membranes compared with the rigid based ones as demonstrated by TEM. As a result, given the same swelling ratio, hydroxide conductivity of the semi-flexible polymer membrane was about 2-fold higher than the one of the rigid polymer based membrane (e.g., 45 vs. 22 mS cm−1 with the same swelling ratio of 24% at 20 °C). The highest achieved conductivity for the semi-flexible polymer membranes at 60 °C was 93 mS cm−1, which was much higher those of other random poly (aryl ether sulfone) based imidazolium AEMs (27–81 mS cm−1). The single cell employing the semi-flexible polymer membrane exhibited a maximum power density of 125 mW cm−2 which was also higher than those for other random poly (aryl ether sulfone) based imidazolium AEMs (16–105.2 mW cm−2).

Abstract IA29: Towards synthetic immune cells for cancer immunotherapy

Abstract Most cellular therapies targeting cancer require culture of autologous cells. The dedicated facilities and personnel needed, the variability in quality of the product depending on the condition of the patient and state of disease, hamper widespread use. In an attempt to generate an of the shelf product to target cancer we exploited the ever expanding possibilities to build supramolecular structures offered by chemistry to mimic nature including the construction of artificial immune cells or functions thereof. Effective immunotherapy critically depends on efficient production of antigen-specific cytotoxic T-cells. Herein lies an opportunity for both chemists and immunologists to design and synthesize so-called artificial antigen presenting cells (aAPCs) that can generate in vivo T-cell expansion. We have designed a novel synthetic dendritic cell (sDC) that possesses essential features of natural DCs. Our sDC is based on a semi-flexible poly(isocyano peptide) polymer and, as proof of principle, carries both anti-CD3 antibodies for triggering the T cell receptor/CD3 complex as well as anti-CD28 antibodies as a co-stimulatory signal. Multiple copies of both antibodies facilitate multivalent binding similar to natural DCs. The high mobility of these polymer-bound antibodies, reminiscent of protein motility in a natural plasma membrane, enables receptor rearrangements to occur during T cell activation. We observed effective T cell activation at significantly lower antibody concentrations than freely soluble antibodies. We also demonstrate antigen specific T cell activation when MHC/peptide complexes were bound. These findings demonstrate the potential of multifunctional polymers for mimicking functions of natural DCs or other immune cells, paving the way for their exploitation in immunotherapeutic strategies. Citation Format: Carl G. Figdor, Subhra Mandal, Roel Hammink, Loek Eggermont, Jorieke Weiden, Dion Voerman, Jurjen Tel, Zaskia H. Eksteen-Akeroyd, Kerstin Blank, Alan E. Rowan. Towards synthetic immune cells for cancer immunotherapy. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr IA29.

Polymer-based synthetic dendritic cells for tailoring robust and multifunctional T cell responses.

Dendritic cells (DCs) are antigen-presenting cells that play an essential role in T cell activation. Recent efforts in cancer immunotherapy have been directed at the development of artificial antigen presenting cells (aAPCs) loaded with tumor antigens. These aAPCs are designed to mimic DCs with the goal of triggering an efficient and specific T cell response directed against the tumor. We have designed a novel synthetic dendritic cell (sDC) that possesses the essential features of natural DCs. Our sDC is based on a semiflexible poly(isocyano peptide) polymer and carries anti-CD3 antibodies (αCD3) for triggering the T cell receptor/CD3 complex as well as anti-CD28 antibodies (αCD28) as a co-stimulatory signal. Multiple copies of both antibodies facilitate multivalent binding similar to natural DCs. The high mobility of these polymer-bound antibodies, reminiscent of protein motility in a natural plasma membrane, enables receptor rearrangements to occur during T cell activation. We show that our bifunctional αCD3/αCD28-sDC triggers T cell activation at significantly lower antibody concentrations than freely soluble antibodies. This superior performance is further demonstrated in comparison to a mixture of monofunctional αCD3-sDC and αCD28-sDC. The presence of both antibodies on the same polymer not only reduces the threshold for T cell activation but, more importantly, critically shapes the specificity of the T cell response. αCD3/αCD28-sDC is a far more efficient activator of multifunctional killer cells. These findings demonstrate the potential of multifunctional polymers for mimicking natural DCs, paving the way for their exploitation in immunotherapeutic strategies.

Self-Diffusion of a Semiflexible Polypeptide in a Magnetically Aligned Liquid Crystalline Phase

The tracer self-diffusion coefficient of semiflexible poly(γ-benzyl-α,L-glutamate) with a length of ∼160 nm and a diameter of ∼1.6 nm is determined by fluorescence photobleaching recovery in the magnetically aligned liquid crystalline phase. The rate of diffusion in the direction of molecular alignment declines with concentration in the liquid crystalline phase, while the rate perpendicular to the direction of molecular alignment remains approximately constant. At concentrations just sufficient to sustain the liquid crystalline phase, the parallel diffusion exceeds the perpendicular diffusion by a factor of almost 5. This ratio declines to as little as 2 at higher concentrations. Comparisons are made with previous studies on other systems ranging from rigid virus particles to small mesogens.

Polymer Depletion-Induced Instability of Silica Suspensions in the Presence of Flexible and Semiflexible Polymers

Polymer depletion-induced instability of silica suspensions in dilute toluene solutions of flexible polystyrene (PS) or semiflexible poly(hexyl isocyanate) (PHIC) was investigated by direct observation and oscillatory moduli measurements as functions of silica volume fraction and polymer molecular weight. Addition of the respective polymers to the gelled silica suspensions induces a gel settling. Below the silica volume fraction φ=4 vol%, PS chains compress the volume of the sediment silica phase, whereas PHIC chains expand it and play a role in swelling agents. Thus, PHIC chains lead to the formation of aggregates in the silica suspensions that are larger and less compact than those formed by the PS chains. On the other hand, above φ=4 vol% where the silica suspension occurs gelation, the effect of nonadsorbing polymers on changes in the volume of the silica phase is opposite. Moreover, polymer depletion interaction results in a mechanically stronger gelled phase, leading to the storage modulus G′ values larger than those without polymer, but the effects of polymer concentration and polymer molecular weight on the G′ values are not clear.

Small-Angle X-ray Scattering Studies of Poly(arylethinylene): Molecular Conformation in Solution and Orientational Ordering in Rod−Coil Ionomer Blends

Poly(pyridyl/phenyl-ethinylene) polymers of tuned rigidity/flexibility were synthesized and their molecular conformations in solution determined by small-angle X-ray scattering. These polymers were used as molecularly dispersed reinforcing components in ionomer blends with partially sulfonated polystyrene. Homogeneous ionomer blends were formed by acid−base interactions between the two blend components. Small-angle X-ray scattering revealed that in the case of rodlike or semiflexible poly(pyridyl/phenyl-ethinylenes) an elongation-induced orientational ordering is obtained. However, blend samples prepared with flexible poly(pyridyl/phenyl-ethinylene) polymers do not show any observable orientation. The orientation parameter varied systematically with the rigidity/flexibility of the reinforcing component, as did the Young modulus determined from stress−strain measurements.

Moisture-induced stress relaxation of polyimide thin films

Four different polyimides: rodlike poly(p-phenylene pyromellitimide) (PMDA-PDA), pseudo-rodlike poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA), semiflexible poly(4,4-oxydiphenylene pyromellitimide) (PMDA-ODA) and poly(4,4-oxydiphenylene biphenyltetracarboximide) (BPDA-ODA) were prepared from two different precursors, poly(amic diethyl ester) (PAE) and poly(amic acid) (PAA). For polyimides prepared from the PAE precursors, stress relaxation coefficient at 25°C, 100% RH was 14.76×10−10cm2/s for PMDA-PDA, 3.29×10−10cm2/s for BPDA-PDA, 24.91×10−10cm2/s for PMDA-ODA and 9.34×10−10cm2/s for BPDA-ODA. For polyimides prepared from the PAA precursors, stress relaxation coefficient at 25°C, 100% RH was 10.50×10−10cm2/s for PMDA-PDA, 1.91×10−10cm2/s for BPDA-PDA, 28.84×10−10cm2/s for PMDA-ODA and 9.10×10−10cm2/s for BPDA-ODA. The effect of bulky ethyl ester group on the stress relaxation behavior is significantly high in rodlike PMDA-PDA or pseudo-rodlike BPDA-PDA having high chain rigidity and intermolecular packing order. The decreased birefringence, crystallinity and the looser packing in amorphous region of rigid polyimide derived from PAE may induce fast stress relaxation compared to flexible polyimide. Specially, the different chain mobility of polyimide also induced significant effect on the stress relaxation.

Stress behaviors and thermal properties of polyimide thin films depending on the different curing process

The effect of high boiling point solvent on the residual stress behaviors of semiflexible structure poly(4,4′-oxydiphenylene pyromellitimide) (PMDA-ODA) and pseudo-rodlike poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA) polyimide was investigated. As a solvent, a mixed solution of 20 wt % cyclohexyl-2-pyrrolidone (CHP; bp = 307 °C) and 80 wt % n-methyl-2-pyrrolidone (NMP; bp = 202 °C) was used. The effects of solvent system and imidizing history on the morphological structure, as well as residual stress, were significantly high in the BPDA-PDA having high chain rigidity, but relatively low in the semiflexible PMDA-ODA with low chain rigidity. In addition, rapidly cured films prepared from PAA (NMP/CHP) showed higher residual stress and a lower degree of molecular anisotropy than slowly cured film imidized from PAA (NMP). This was induced by high chain mobility in polyimide thin films prepared from PAA (NMP/CHP) during the thermal cure process. Therefore, molecular anisotropy, depending on the solvent system and imidizing history, might be one of the important factors leading to low residual stress in polyimide thin films. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2879–2890, 2000

Effects of precursor origins on water sorption behaviors of various aromatic polyimides in thin films

Poly(amic diethyl ester) [PAE] precursors of four different polyimides with various chain rigidities were synthesized and thermally converted to the polyimides in thin films: rodlike poly( p-phenylene pyromellitimide) [PMDA-PDA] and poly(4,4′-biphenylene pyromellitimide) [PMDA-BZ], pseudo-rodlike poly( p-phenylene biphenylenetetracarboximide) [BPDA-PDA] and semiflexible poly(4,4-oxydiphenylene pyromellitimide) [PMDA-ODA PAE]. For the polyimide films, water sorption behaviors were investigated by gravimetry and then compared with those of the polyimides prepared from the corresponding poly(amic acid) [PAA] precursors. In addition, their morphological structures were examined by X-ray diffraction. For all the polyimides, both water sorption and morphological structure were dependent upon the history of precursor origin. All the polyimides except PMDA-ODA revealed relatively higher diffusion coefficient of water, higher water sorption, lower intermolecular packing order and lower population of a more ordered phase in the PAE-derived polyimide films than the corresponding PAA-derived polyimide films. For PMDA-ODA, the variations in the water diffusion and sorption due to the precursor origin were relatively small in spite of a relatively large change in the morphological structure. Overall, the effect of precursor origin on the water diffusion and sorption is significantly high in the rodlike or pseudo-rodlike polyimides having a high chain rigidity and high intermolecular packing order, but relatively low in the semiflexible polyimide with a relatively low chain rigidity. In comparison, regardless of the precursor origins, the diffusion coefficient of water was in the decreasing order PMDA-ODA>PMDA-PDA>PMDA-BZ>BPDA-PDA and, however, the water sorption was in the decreasing order PMDA-PDA>PMDA-BZ>PMDA-ODA>BPDA-PDA. These water diffusion and sorption behaviors were understood by considering their chemical affinities to water in addition to the morphological structures.

Water sorption and diffusion behaviours in thin films of photosensitive polyimides

Several photosensitive polyimide (PSPI) precursors were synthesised by the acid/base complexations of conventional poly(amic acid) precursors with photochemically cross-linkable 2-(dimethylamino)ethyl methacrylate. PSPIs in films were prepared from the photosensitive precursors by thermal imidisation, whereas the corresponding PIs in films were prepared from the conventional poly(amic acid)s: rod-like poly(p-phenylene pyromellitimide) (PMDA-PDA), rigid (poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA), semi-flexible poly(4,4′-oxydiphenylene biphenyltetracarboximide) (BPDA-ODA), semi-flexible poly(4,4′-oxydiphenylene pyromellit-imide) (PMDA-ODA), and flexible poly(4,4′-oxydiphenylene benzophenonetetracarboximide) (BTDA-ODA). Water sorption and diffusion behaviours in the PSPIs were gravimetrically measured at 25°C in 100% relative humidity and compared with those of the corresponding PIs. For the PSPIs as well as the PIs, the water sorption and diffusion behaviours were nearly Fickian, regardless of the backbone chemistry. However, those were strongly dependent upon the polyimide backbone chemistry and precursor origin. In addition, those in polyimides were affected by the bulky photosenistive groups, even though they were temporarily linked to the precursor polymers and then debonded from the backbones and ultimately outgassed during the thermal imidisation process. For PMDA-PDA, BPDA-PDA and BPDA-ODA, the PSPIs absorbed water more quickly than the corresponding PIs, whereas for PMDA-ODA and BTDA-ODA, the PSPIs absorbed water less quickly than the corresponding PIs. In contrast to the water diffusion, all the PSPIs absorbed slightly more or a great deal more water than the corresponding PIs, depending on the backbone chemistry. All the measured water sorption and diffusion behaviours in the PSPIs were understood by considering changes in the morphological structure (namely, chain order and orientation), voids, and residues possibly induced by the bulky photosensitive groups, in addition to the Tg as well as the chemical affinity to water.

The effects of hydrogen bonding on the liquid crystalline behavior of semiflexible poly(urethaneester)s

AbstractThe peculiar liquid crystalline behavior of two poly(urethane‐ester)s TDI‐C6C4 and TDI‐C6C8 is reported. Evidence is provided of the formation of two nematic mesophases, a cybotactic nematic and a conventional nematic mesophase, in TDI‐C6C8 and of one cybotactic nematic mesophase in TDI‐C6C4. IR spectroscopy indicates that different hydrogen bonded and non‐bonded structures occur with varying temperature. The transition from the nematic cybotactic mesophase to the nematic mesophase, or to the isotropic phase, is accompanied by a substantial decrease of the strength of the hydrogen bonds. This is also reflected in the dynamic‐mechanical behavior of these poly(urethane‐ester)s which is similar to the one of slightly crosslinked thermoreversible networks.

Influence of side-chain bearing units on the phase behaviour of a series of copoly(ester ether)s

Appending a short flexible side-chain to a semiflexible poly(ester ether) results in substantial changes to the phase behaviour; in particular, where comparisons are possible, there is a considerable reduction in the phase transition temperature for the side-chain-bearing system compared to the unsubstituted polymer. A further difference was seen in the tendency for liquid crystal phase formation; side-chain containing systems exhibit liquid crystalline behaviour over a relatively broad temperature range. This may be, at least in part, related to the differing tendencies of the two systems towards crystallization. A non-side-chain substituted polymer is, albeit partly, crystalline at room temperature; in contrast, the side-chain substituted polymer is mainly amorphous. On varying the side-chain concentration in the copolymer, a systematic change in phase behaviour is revealed. The effect of copolymerization on the phase transition temperature is discussed and a comparison with similar copolymers without side-chains reveals the importance of geometric over statistical constraints on the formation of the solid phase.

Dynamic light scattering from a semiflexible polymer at very low concentrations

Dynamic light scattering measurements on semiflexible poly(γ-benzyl-α,L-glutamate) have been performed at very low concentrations, near the limit for reliable multiangle detection, in N,N-dimethylformamide. By several methods of data analysis, the mutual diffusion coefficient Dm is initially level or slightly decreasing with polymer concentration. It then increases substantially, as expected in a good solvent. Static light scattering measurements offer no thermodynamic explanation for the initially level or decreasing behavior, which is apparently a manifestation of the decrease in lateral mobility as the rods become entangled in semidilute solutions. The coefficient C describing the dependence of the first cumulant of the electric field autocorrelation function upon squared scattering vector decreases with concentration, even in the most dilute regime measured. The reliability of persistence lengths estimated for this polymer by dynamic light scattering is considered.

Orientational Characteristics of Semiflexible Poly(yne)–Platinum Polymers as Studied by Deuterium NMR

Orientational Characteristics of Semiflexible Poly(yne)–Platinum Polymers as Studied by Deuterium NMR

Chiral liquid‐crystalline polymers. XI. Thermotropic behavior and chiroptical properties in solution of a new series of optically active poly (ester β‐sulfide)s

AbstractThe synthesis and characterization are described of a series of optically active semiflexible poly(ester β‐sulfide)s 6*Sn with repeating units constituted by two p‐oxybenzoyl diads spaced in an alternating fashion by a sulfide‐containing polymethylene segment of variable length (n = 2‐10) and a chiral (R)‐3‐methylhexanediyl segment of high enantiomeric purity. The polymers were prepared with good yields and relatively high molecular weights and narrow degrees of dispersity by a Michael‐type polyaddition reaction of bis‐thiols to the same chiral mesogenic bisacrylate monomer. Data are reported on the characterization of their chiroptical properties in dilute solution and thermal‐optical properties in the bulk, with attention being devoted to the distinct odd‐even alternations of the cholesteric‐isotropic melt transition parameters. A comparison of the mesomorphic behavior and relevant thermodynamic quantities is presented between the present series of polymers and the achiral analogues of series 6Sn as well as the chiral, positional isomers of series mS6*. The dependence of the overall properties and their trends on very subtle structural changes is stressed, thus highlighting the critical interconnection between mesogenic cores and spacer segments in semiflexible liquid‐crystalline polyesters.

Dilute solution properties of semiflexible poly(substituted methylenes): intrinsic viscosity of poly(diisopropyl fumarate) in benzene

La relation [n]=7,53•10 −6 •M 0,98 est etablie entre la viscosite intrinseque du polyfumarate en solution dans le benzene a 30 o C et sa masse moleculairie pour M<3•10 5 . La valeur de a obtenue (0,98) est la plus elevee obtenue pour un polymere vinylique; elle diminue lorsque la masse moleculaire augmente et depend de la nature des groupes alkyl (0,87 pour le poly(fumarate de diethyle))

Reactivity in radical polymerization ofN-substituted maleimides and thermal stability of the resulting polymers

The effect ofN-substituents on the radical polymerization ofN-substituted maleimides (RMI) was investigated. The polymerization reactivities, i.e. yield and molecular weight of the polymers, were found to change depending on the structure of theN-substituents. The poly(RMI)s bearing a bulkyN-substituent were confirmed to be semiflexible poly(substituted methylene)s which were soluble in many organic solvents, but did not melt below their decomposition temperatures. From thermogravimetric analysis determined in a nitrogen stream, no weight-loss of poly(RMI) was observed at temperature below 300°C, and the maximum decomposition temperature was 400–440°C, except forN-tert-alkyl substituted derivatives which decomposed at 240–280°C via a two-step reaction.

Molecular order in condensed states of semiflexible poly(amic acid) and polyimide

Ordre moleculaire du polyacide oxydiphenylene-4,4' pyromellitamique et du polyimide correspondant