Nonmigratory internal plasticization of poly(vinyl chloride) via pendant triazoles bearing alkyl or polyether esters

Branched and linear nonmigratory internal plasticizers attached to PVC by a pendant triazole linkage were synthesized and investigated. Copper-free azide-alkyne thermal cycloaddition was employed to covalently bind triazole-based phthalate mimics to PVC. To systematically investigate the effect of plasticizer structure on glass transition temperature, several architectural motifs were explored. Free volume theory was considered when designing many of these internal plasticizers: hexyl-tethers were utilized to generate additional space between the triazole-phthalate mimic and the polymer backbone. Miscibility of these triazole-plasticizers in PVC is important: variation of the ester moieties on the triazole possessing alkyl and/or poly(ethylene oxide) chains produced a wide range of glass transition temperatures (T_g): from anti-plasticizing 96 °C, to highly efficient plasticized materials exhibiting T_g values as low as −42 °C. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2397–2411     

Effect of alkyl side chain length on the properties of polyetherimides from molecular simulation combined with experimental results

Three polyetherimides (PEIs) with the same backbone of Ultem 100 but different lengths of the alkyl side chains were simulated by using molecular dynamics and molecular mechanics techniques to investigate the effect of side chain length on their properties and physical mechanism behind. Simulation results, which are consistent to the experimental data, show that PEI‐5 with four methylene units in each alkyl side chain has higher T_g (glass transition temperature) and higher tensile strength, but lower tensile elongation at break than those of PEI‐6 with five and PEI‐8 with seven methylene units in each alkyl side chain. However, unlike the traditional phenomena, conformational analysis provides that PEI‐5 with the highest T_g gives the highest flexibility to the polymer chain, whereas PEI‐8 with the lowest T_g imparts the lowest flexibility resulting from attachment of longer alkyl side chain increase the rigidity of backbone. From the calculated ratio of the accessible volume to the total volume for each system, the highest ratio of PEI‐8 indicates that long alkyl side chains generate more free volume than short side chains, acting as an internal plasticizer in bulk structure. It is the internal plasticizing effect that is predominantly responsible for the abnormal properties, instead of the rigidity from side chains. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 595–599, 2010     

Viscoelastic characteristics of plasticized cellulose nanocomposites

The plasticization effects of cellulose diacetate composite systems including nanoparticles (montmorillonite, MMT) and plasticizers(diethyl phthalate, DEP) were investigated by the time–temperature superposition technique and viscoelastic modeling. Exhibiting the highest modulus value in the glass state, the viscoelastic modulus of the MMT nanocomposite rapidly decreased above the glass‐transition temperature (T_g). The Arrhenius‐type activation energy of pristine cellulose acetate showed the lowest value of activation energy and both DEP‐plasticized and MMT‐reinforced systems exhibited increased values of activation energy. Although the free volume fraction at the T_g decreased with the plasticizer content, it increased with the incorporation of MMT, seemingly preventing the polymer chains from being arranged in an ordered structure. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 59–65, 2005     

Amorphous copolyesters based on bibenzoic acids and neopentyl glycol

High T_g amorphous copolyester thermoplastics were synthesized by incorporating 4,4′‐bibenzoate (4,4′BB) and 3,4′‐bibenzoate moieties into the polyester backbone via melt polycondensation. The high levels of crystallinity typically associated with 4,4′BB containing polyesters were suppressed through copolymerization of ethylene glycol, 1,4‐cyclohexane dimethanol, and neopentyl glycol (NPG) diols. NPG was shown to be highly effective in suppressing crystallization and was used to produce amorphous compositions with T_g’s as high as 129 °C. Diol ratios were determined by ¹H NMR spectroscopy and molecular weights were assessed with inherent viscosity (η_inh). Thermogravimetric analysis showed single‐step weight losses in the range of 395 – 419 °C. Differential scanning calorimetry was used to determine melting points and glass transition temperatures over a wide range of copolyester compositions and identified amorphous compositions. Dynamic mechanical analysis confirmed T_g’s and was used to study β‐relaxations below the T_g. Rheological analysis revealed the effect of NPG structures on shear thinning and thermal stability. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 579–587     

Designing anti-migration furan-based plasticizers and their plasticization properties in poly (vinyl chloride) blends

The use of bio-based plasticizers with low toxicity and good compatibility with polyvinyl chloride (PVC) has attracted more attention in the recent years. With bio-based 2, 5-furandicarboxylic acid (FDCA) and butyl oligo-glycol ethers as raw materials, three liquid furan-based plasticizers of di(butyl glycol) furan-2,5-dicarboxylate, di(butyldiglycol) furan-2,5-dicarboxylate and di(butyltriglycol) furan-2,5-dicarboxylate were synthesized by direct esterification. The chemical structure of three plasticizers was characterized with FTIR, ¹H NMR and ¹³C NMR. From DMA measurement, the glass transition temperature (T_g) of the plasticized PVC was decreased gradually when furan-based plasticizers were added to PVC formulation from 30 up to 50 phr. Due to lots of ether bonds in furan-based plasticizers, they expressed over two-fold lower migration in organic solvent compared with the traditional plasticizer diethylhexyl phthalate (DEHP). Through the characterization of elongation at break, hardness and thermal stability, furan-based plasticizers presented the same plasticization properties as DEHP, and had potential industrial application prospects.     

Effect of endgroup modification on dynamic viscoelastic relaxation and motion of hyperbranched poly(ether ketone)s

Fluoro‐terminated hyperbranched poly(ether ketone) (FHPEK) was synthesized and its end groups were modified with alkyl compounds of different chain lengths, i.e., hexyloxy (C6), dodecyloxy (C12), and octadecyloxy, (C18), to produce alkyl‐modified HPEKs (HPEK‐C6, HPEK‐C12, and HPEK‐C18, respectively). Master curves were constructed by using the time‐temperature superposition principle. The horizontal shift factors, a_T, used for the construction of the master curves were fit using the William‐Landel‐Ferry (WLF) equation. From the fitting parameters, the apparent activation energy, E_a, was estimated. With increasing alkyl chain length, the E_a values were found to decrease in the order FHPEK > HPEK‐C6 > HPEK‐C12, and then increase for HPEK‐C18. The average relaxation time, τ_HN, was determined by fitting of the dynamic moduli G′(ω) and G″(ω) to the empirical Havriliak‐Negami equation. Similarly, the τ_HN values decreased in the order of FHPEK > HPEK‐C6 > HPEK‐C12, and then increased for HPEK‐C18. This indicates that the endgroup modification with short alkyl chains (C6, C12) increased the molecular mobility due to the internal plasticization effect of these alkyl chains. Modification with the longer alkyl chain (C18) retarded the molecular motion through an antiplasticization effect caused by summation of nonpolar hydrophobic interactions between long hydrocarbon chains. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2079–2089, 2008     

Application of a bio‐based polyester plasticizer modified by hydrosilicon‐hydrogenation reaction in soft PVC films

A kind of bio‐based plasticizer, poly (hexanediol maleic) (MH), was synthesized using 1,6‐hexalene and maleic acid as raw materials, and it was modified by hydrosilicon‐hydrogenation reaction to improve its plasticizing efficiency. The chemical structure and plasticizing performance of MH and its modification product (MHA) were characterized by Fourier‐transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (¹H‐NMR), X‐ray photoelectron spectroscopy (XPS), and Dynamic mechanical analysis (DMA). It was found that the hydrosilicon‐hydrogenation modification effectively improved the plasticizing efficiency of MH, reflecting on the decreased T_g and the increased elongation at break of PVC blends. The migration resistance of PVC blends was tested and analyzed by solubility parameters, which revealed that the migration stabilities of PVC blends were promoted after modification. It was verified that the hydrogen bonding interaction between the C?O group of plasticizers and α‐hydrogen of PVC exhibited in FTIR analysis was the main reason for the improvement of plasticizer performance of MH. Moreover, a new hydrogen bonding formed between Si? O? Si of MHA and the α‐hydrogen of PVC derived from XPS also caused the further improvement of plasticity for MHA.     

Plasticization of amorphous perfluoropolymers

Poly(perfluoro‐4‐vinyloxy‐1‐butene), which is also known as Cytop, and poly[4,5‐difluoro‐2,2‐bis(trifluoromethyl)‐1,3‐dioxole]‐co‐poly(tetrafluoroethylene) copolymers with dioxole monomer contents of 65% or 87% (known as Teflon AF1600 and Teflon AF2400, respectively) were plasticized with four fluorous compounds. While plasticization of all polymers with perfluoroperhydrophenanthrene, perfluoro(1‐methyldecalin), a perfluorotetraether with three trifluoromethyl side groups and one hydrogen atom, and a linear perfluorooligoether with an average of 14.3 ether groups per molecule was successful, these four plasticizers affected the 12 blends very differently. A threshold of plasticization beyond which further increases in the plasticizer volume fraction did not further affect the glass transition temperature, T_g, was observed for some blends. Also, the limit of miscibility ranged from as low as 20% plasticizer content to complete miscibility at all volume fractions. The blends of Teflon AF2400 or Teflon AF1600 with high contents of the oligoether provided T_g values as low as ?114 °C, lower than for any other fully miscible blend. The occurrence of two glass transitions in an intermediate range of plasticizer volume ratios for these two types of blends can be explained by distinct local environments rather than macroscopic phase separation, as anticipated by the Lodge‐McLeish model. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 516–525, 2008     

Revisiting the crystallization of poly(2‐alkyl‐2‐oxazoline)s

Poly(2‐alkyl‐2‐oxazoline)s (PAOx) exhibit different crystallization behavior depending on the length of the alkyl side chain. PAOx having methyl, ethyl, or propyl side chains do not show any bulk crystallization. Crystallization in the heating cycle, that is, cold crystallization, is observed for PAOx with butyl and pentyl side chains. For PAOx with longer alkyl side chains crystallization occurs in the cooling cycle. The different crystallization behavior is attributed to the different polymer chain mobility in line with the glass transition temperature (T_g) dependency on alkyl side chain length. The decrease in chain mobility with decreasing alkyl side chain length hinders the relaxation of the polymer backbone to the thermodynamic equilibrium crystalline structure. Double melting behavior is observed for PButOx and PiPropOx which is explained by the melt‐recrystallization mechanism. Isothermal crystallization experiments of PButOx between 60 and 90 °C and PiPropOx between 90 and 150 °C show that PAOx can crystallize in bulk when enough time is given. The decrease of T_g and the corresponding increase in chain mobility at T > T_g with increasing alkyl side chain length can be attributed to an increasing distance between the polymer backbones and thus decreasing average strength of amide dipole interactions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 721–729     

Synthesis and polymerization of new di‐octadecyl ester derivatives of α‐hydroxymethyl acrylate: A structure‐property correlation for their copolymers with methyl methacrylate

New ether dimer (ED‐Od) and diester (ODE) derivatives of α‐hydroxymethylacrylate, each having two octadecyl side chains, were synthesized and (co)polymerized to evaluate the effects of differences in the structures of the monomers on final (co)polymer properties, particularly glass transition temperature. The free radical polymerizations of both monomers yielded high‐molecular weight polymers. Cyclopolymer formation of ED‐Od was confirmed by ¹³C NMR analysis and the cyclization efficiency (0.95 or greater) was found to be as high as the cyclization efficiencies of the cyclopolymerizations of ether dimers of various alkyl α‐hydroxymethylacrylates synthesized previously. Copolymers of both ED‐Od and ODE with methyl methacrylate (MMA) showed significant T_g decreases over PMMA due to octadecyl side groups causing “internal” plasticization. Comparison of the T_g's of the copolymers of octadecyl methacrylate, ED‐Od and ODE with MMA revealed that the impacts of these monomers on depression of T_g's are identical. That is, the magnitude of decrease in T_g's was quantitatively related to the number of the octadecyl side groups in the copolymers rather than their placement on the same or randomly incorporated repeat units. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7785–7793, 2008     

Free volume,glass transition,and degree of branching in metallocene‐based propylene/α‐olefin copolymers: Positron lifetime,density, and differential scanning calorimetric studies

Positron annihilation lifetime spectroscopy (PALS), density, and differential scanning calorimetric (DSC) measurements were used to study systematically the variation of the glass‐transition temperature (T_g) and the size v and number density N_h of local free volumes in n‐alkyl‐branched polypropylenes. The samples were metallocene‐catalyzed propylene copolymers with different α‐olefins (from C₄ to C₁₆) and a different α‐olefin content (between 0 and 20 mol %). From the total specific volume and crystallinity the specific volume of the amorphous phase V_a was estimated and used to calculate the fractional free (hole) volume h and value of N_h. The variations of T_g, v, V_a, h, and N_h were related to the degree (number and length) of branching. T_g decreases and v increases linearly with the number and length of n‐alkyl branches. This behavior was attributed to an increased segmental mobility caused by branching. Both values, T_g and v, follow linear master curves as a function of the degree of branching (DB) if this is defined as the number of all side‐chain carbons with respect to a total of 1000 (main‐chain and side‐chain) carbons. Only propylene/1‐butene copolymers deviated from these relations. A linear relation between v and T_g was also found. The number density of holes was estimated to be N_h = 0.49(±0.07) nm^?3 and N_h′ = 0.58(±0.11) × 10²¹ g^?1, respectively. It shows a slight variation with the DB, which is also seen in the behavior of the specific volume V_a. This variation was explained by the appearance of sterical hindrances resulting from short‐chain branches that may prevent an efficient packing of the chains. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 434–453, 2002; DOI 10.1002/polb.10108     

Ionic liquids: New generation stable plasticizers for poly(vinyl chloride)

Room temperature ionic liquids (ILs), based on ammonium, imidazolium and phosphonium cations, were studied as novel plasticizers for poly(vinyl chloride), PVC. All the ILs tested were able to produce flexible PVC. Upon 20 wt% plasticization, some of the ILs lowered the glass transition temperature (T_g) of PVC more than that done by several traditional plasticizers. They showed good thermodynamic compatibility as well. Several ILs showed better leaching and migration resistance than the traditional plasticizers. This was, in particular, a significant observation considering the ongoing controversy regarding the leaching and migration issues of the commonly-used phthalate plasticizers. High temperature and ultraviolet (UV) ray stability of IL-plasticized PVC samples were also studied.     

Synthesis of hydroxyl‐bearing polyurethanes from naturally occurring myo‐inositol

A route from naturally occurring myo‐inositol to hydroxyl‐bearing polyurethanes has been developed. The diol prepared from the bis‐acetalization of myo‐inositol with 1,1‐dimethoxycyclohexane was reacted with a rigid diisocyanate, 1,3‐bis(isocyanatomethyl)cyclohexane to afford the corresponding polyurethane, of which glass transition temperature (T_g) was quite high as 192 °C. The polyurethane contains side chains inherited from the acetal moieties of the diol monomer and was treated with trifluoroacetic acid to hydrolyze the acetal moieties and afford the target polyurethane functionalized with hydroxyl groups. The presence of many hydroxyl groups in the side chains, which can form hydrogen bonds with each other, resulted in a high T_g, 186 °C. In addition, the hydroxyl groups were reacted with isocyanates to achieve further side‐chain modifications. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1358–1364     

Branched plasticizers derived from eugenol via green polymerization for low/non-migration and externally/internally plasticized polyvinyl chloride materials

The synthesis of nontoxic plasticizers derived from the waste residues of the rosin-processing industry can reduce pollution and promote the high-value utilization of the waste residues of rosin. In this study, four kinds of sustainable branched plasticizers derived from a biomass resource, eugenol (derived from the waste residues of the rosin processing industry), were synthesized via one-pot solvent free polymerization and used to plasticize polyvinyl chloride (PVC). Internally plasticized PVC was fabricated using thiolated DPE (branched plasticizers based on eugenol). The thermal stability, tensile properties, microstructure, volatility behavior, and solvent extraction resistance of plasticized PVC were investigated. Compared with the behavior of the commercial plasticizer dioctyl phthalate, the thermal stability, plasticizing efficiency, and migration resistance of the branched plasticizers are superior. The acute oral toxicity dose of each branched plasticizer was extremely high at 5000 mg/kg of body weight, with no deaths among test animals. Compared with externally plasticized PVC, the internally plasticized PVC showed zero weight loss in volatility and leaching tests despite its less effective plasticization. All the branched plasticizers have potential application in plastic products.     

Segmented block copolyesters using click chemistry

Copper(I) catalyzed azide‐alkyne 1,3‐Huisgen cycloaddition reaction afforded the synthesis of triazole‐containing polyesters and segmented block copolyesters at moderate temperatures. Triazole‐containing homopolyesters exhibited significantly increased (～40 °C) glass transition temperatures (T_g) relative to high temperature, melt synthesis of polyesters with analogous structures. Quantitative synthesis of azido‐terminated poly(propylene glycol) (PPG) allowed for the preparation of segmented polyesters, which exhibited increased solubility and mechanical ductility relative to triazole‐containing homopolyesters. Differential scanning calorimetry demonstrated a soft segment (SS) T_g near ?60 °C for the segmented polyesters, consistent with microphase separation. Tensile testing revealed Young's moduli ranging from 7 to 133 MPa as a function of hard segment (HS) content, and stress at break values approached 10 MPa for 50 wt % HS segmented click polyesters. Dynamic mechanical analysis demonstrated an increased rubbery plateau modulus with increased HS content, and the T_g's of both the SS and HS did not vary with composition, confirming microphase separation. Atomic force microscopy also indicated microphase separated and semicrystalline morphologies for the segmented click polyesters. This is the first report detailing the preparation of segmented copolyesters using click chemistry for the formation of ductile membranes with excellent thermomechanical response. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis,Characterization, and thermoresponsive properties of Helical Polypeptides Derivatized from Poly(γ−4‐(3‐chloropropoxycarbonyl)benzyl‐L‐glutamate)

A series of side‐chain‐functionalized α‐helical polypeptides, i.e., poly(γ‐4‐(3‐chloropropoxycarbonyl)benzyl‐_L‐glutamate) (6) have been prepared from n‐butylamine initiated ring‐opening polymerization (ROP) of γ‐4‐(3‐chloropropoxycarbonyl)benzyl‐_L‐glutamic acid‐based N‐carboxyanhydride. Polypeptides bearing oligo‐ethylene‐glycol (OEG) groups or 1‐butylimidazolium salts were prepared from 6 via copper‐mediated [2+3] alkyne‐azide 1,3‐dipolar cycloaddition or nuleophilic substitution, respectively. CD and FTIR analysis revealed that the polymers adopt α‐helical conformations both in solution and the solid state. Polymers bearing OEG (m = 3) side‐chains showed reversible LCST‐type phase transition behaviors in water while polymers bearing 1‐butylimidazolium and I^? counter‐anions exhibited reversible UCST‐type transitions in water. Variable‐temperature UV‐vis analysis revealed that the phase transition temperatures (T_pts) were dependent on the main‐chain length and polymeric concentration. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2469–2480     

Preparation and functionalization of linear and reductively degradable highly branched cyanoacrylate‐based polymers

Ethyl cyanoacrylate (ECA) was polymerized radically in the presence of small amounts of trifluoroacetic acid as effective inhibitor of incidental anionic polymerization. Methyl methacrylate and other functional vinyl monomers (e.g., 2‐chloroethyl and 2‐bromoethyl methacrylate) were copolymerized with ECA, yielding linear ECA‐rich copolymers, which could readily undergo further modifications, for instance nucleophilic substitution with azide. In the presence of a disulfide‐containing dimethacrylate crosslinker and a chain transfer agent (CBr₄) during the free radical copolymerizations of ECA with methacrylates, highly branched ECA‐based polymers containing disulfide groups at the branching points were obtained prior to gelation. The polymers degraded upon addition of reducing agents. The prepared polymers, which contained peripheral (chain end) alkyl bromide groups as well as pendant alkyl chloride or bromide groups were then reacted with sodium azide, affording azide‐containing polymers that were reacted with functional alkynes under copper‐catalyzed “click” chemistry conditions. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3683–3693     

Precise synthesis of a series of poly(4‐n‐alkylstyrene)s and their glass transition temperatures

Poly(4‐n‐alkylstyrene)s with six kinds of n‐alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and octyl groups covering wide molecular weight range from around 5 k to over 100 k were precisely synthesized by living anionic polymerizations. It was confirmed that all the polymers obtained have narrow molecular weight distribution, that is, M_w/M_n is all less than 1.1, by SEC. T_gs of all the polymers were estimated by DSC measurements and it turned out to be clear that their molecular weight dependence was well described by the Fox–Flory equations. Furthermore, it is evident that T_g monotonically decreases as a number of carbon atoms of n‐alkyl group is increased, though T_g values are all 20 K or more higher than those reported previously for the same polymer series. This is because backbone mobility increases by introducing longer n‐alkyl side groups with high mobility, while T_g difference in between this work and the previous one may due to the experimental conditions and also to the molecular weight range adopted. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 757–763     

Correlating backbone‐to‐backbone distance to ionic conductivity in amorphous polymerized ionic liquids

The morphology and ionic conductivity of poly(1‐n‐alkyl‐3‐vinylimidazolium)‐based homopolymers polymerized from ionic liquids were investigated as a function of the alkyl chain length and counterion type. In general, X‐ray scattering showed three features: (i) backbone‐to‐backbone, (ii) anion‐to‐anion, and (iii) pendant‐to‐pendant characteristic distances. As the alkyl chain length increases, the backbone‐to‐backbone separation increases. As the size of counterion increases, the anion‐to‐anion scattering peak becomes apparent and its correlation length increases. The X‐ray scattering features shift to lower angles as the temperature increases due to thermal expansion. The ionic conductivity results show that the glass transition temperature (T_g) is a dominant, but not exclusive, parameter in determining ion transport. The T_g‐independent ionic conductivity decreases as the backbone‐to‐backbone spacing increases. Further interpretation of the ionic conductivity using the Vogel–Fulcher–Tammann equation enabled the correlation between polymer morphology and ionic conductivity, which highlights the importance of anion hoping between adjacent polymer backbones. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012