New trends in chemical recycling of poly(ethylene terephthalate)

Chemical recycling of poly(ethylene terephthalate) (PET) by nonconventional transesterification and ammonolysis/aminolysis methods are discussed on the basis of literature and own experimental data. The obtained products of deep PET degradation using allylamine (N,N′-diallylterephthaldiamide), triethanolamine and other alkanolamines were prepared and characterized by DSC and elemental analysis.     

Polymeric bis(phosphonomethyl­carboxylato)calcium(II) at 85 K

In the crystal structure of the title compond, alternatively called poly[calcium(II)‐di‐μ‐carboxymethylphosphonato], [Ca(C₂H₄O₅P)₂]_n or [Ca(H₂AP)₂]_n, one of the phosphonate O atoms of the phosphonocarboxylate monoanion lies nearly antiperiplanar (ap) to the carboxylic acid C atom. The phosphonate P atom is located −sc and +ac relative to the carboxylic acid O atoms. The overall structure has a layered architecture. The Ca²⁺ cations lie on a twofold axis and are bridged by the phosphonate O atoms to form chains along the c axis, giving layers parallel to (100). There are medium‐strength O—H⃛O and C—H⃛O hydrogen‐bonding interactions stabilizing the layers, and O—H⃛O hydrogen bonds connect adjacent layers.     

Branched polyether with multiple primary hydroxyl groups: polymerization of 3-ethyl-3-hydroxymethyloxetane

Cationic polymerization of 3-ethyl-3-hydroxymethyloxetane gives branched, soluble macromolecules with multiple glycolic end groups. There are approximately 3–4 “normal” units per one branched unit.     

Synthesis of block copolymers by atom transfer radical polymerization of tert‐butyl acrylate with poly(oxyethylene) macroinitiators

Poly(oxyethylene)s terminated at both ends with 2‐bromopropionate end‐groups were prepared and characterized by means of MALDI TOF mass spectrometry. It was shown, that atom transfer radical polymerization (ATRP) of methyl methacrylate with a poly(oxyethylene) macroinitiator in bulk proceeds with low initiation efficiency while polymerization of tert‐butyl acrylate proceeds with practically quantitative initiation, leading to ABA block copolymers. Originally formed tert‐butyl acrylate blocks contain terminal bromine, as expected for the ATRP mechanism. MALDI TOF analysis indicates, however, that in the later stages of polymerization side reactions lead to elimination of terminal bromine.     

5,5‐Di­methoxy‐2‐phenoxy‐1,3,2‐dioxaphosphorinane 2‐oxide

In the title compound, C₁₁H₁₅O₆P, the six‐membered dioxa­phospho­rinane ring of the cyclic phosphate triester exists in a distorted chair conformation, with the phenoxy group in an axial position. The phenyl ring and both methoxy groups are in a trans–gauche orientation with respect to the 1,3,2‐di­oxa­phospho­rinane ring. In the phosphate group, a significant deformation from the ideal tetrahedral shape is observed. The crystal structure is stabilized by a three‐dimensional network of C—H⋯O interactions.     

Synthesis and EPR Studies of 2′‐Deoxyuridines with Alkynyl,Rodlike Linkages

Sonogashira coupling of diacetyl 5‐ethynyl‐2′‐deoxyuridine with diacetyl 5‐iodo‐2′‐deoxyuridine gave the acylated ethynediyl‐linked 2′‐deoxyuridine dimer ( 3 b ; 63 %), which was deprotected with ammonia/methanol to give ethynediyl‐linked 2′‐deoxyuridines ( 3 a ; 79 %). Treatment of 5‐ethynyl‐2′‐deoxyuridine ( 1 a ) with 5‐iodo‐2′‐deoxyuridine gave the furopyrimidine linked to 2′‐deoxyuridine (78 %). Catalytic oxidative coupling of 1 a (O₂, CuI, Pd/C, N,N‐dimethylformamide) gave butadiynediyl‐linked 2′‐deoxyuridines ( 4 ; 84 %). Double Sonogashira coupling of 5‐iodo‐2′‐deoxyuridine with 1,4‐diethynylbenzene gave 1,4‐phenylenediethynediyl‐bridged 2′‐deoxyuridines ( 5 ; 83 %). Cu‐catalyzed cycloisomerization of dimers 4 and 5 gave their furopyrimidine derivatives. One‐electron addition to 1 a , 3 a , and 4 gave the anion radical, the EPR spectra of which showed that the unpaired electron is largely localized at C6 of one uracil ring (17 G doublet) at 77 K. The EPR spectra of the one‐electron‐oxidized derivatives of ethynediyl‐ and butadiynediyl‐linked uridines 3 a and 4 at 77 K showed that the unpaired electron is delocalized over both rings. Therefore, structures 3 a and 4 provide an efficient electronic link for hole conduction between the uracil rings. However, for the excess electron, an activation barrier prevents coupling to both rings. These dimeric structures could provide a gate that would separate hole transfer from electron transport between strands in DNA systems. In the crystal structure of acylated dimer 3 b , the bases were found in the anti position relative to each other across the ethynyl link, and similar anti conformation was preserved in the derived furopyrimidine–deoxyuridine dinucleoside.     

Porphyrin‐Ryleneimide Hybrids: Low‐Bandgap Acceptors in Energy‐Transfer Cassettes

Energy‐transfer cassettes consisting of naphthaleneimide‐fused metalloporphyrin acceptors (M=Zn and Pd) and BODIPY donors have been designed and synthesized. These systems have rigid pseudo‐tetrahedral structures with a donor‐acceptor separation of ca. 17.5 Å. Spectroscopic investigations, including femtosecond transient absorption measurements, showed efficient excitation energy transfer (EET) occurring according to the Förster mechanism. Strong fluorescence of the donor units and significant spectral overlap of the donor and acceptor subunits are prerequisites for the efficient EET in these systems.     

Exact penalty functions method for mathematical programming problems involving invex functions

In this paper, some new results on the exact penalty function method are presented. Simple optimality characterizations are given for the differentiable nonconvex optimization problems with both inequality and equality constraints via exact penalty function method. The equivalence between sets of optimal solutions in the original mathematical programming problem and its associated exact penalized optimization problem is established under suitable invexity assumption. Furthermore, the equivalence between a saddle point in the invex mathematical programming problem and an optimal point in its exact penalized optimization problem is also proved.     

Optimality and duality for nonsmooth multiobjective programming problems with V-r-invexity

In the paper, we consider a class of nonsmooth multiobjective programming problems in which involved functions are locally Lipschitz. A new concept of invexity for locally Lipschitz vector-valued functions is introduced, called V-r-invexity. The generalized Karush–Kuhn–Tuker necessary and sufficient optimality conditions are established and duality theorems are derived for nonsmooth multiobjective programming problems involving V-r-invex functions (with respect to the same function η).     

柱塞泵油膜压力分析的高效有限单元法

利用有限单元法,数值分析轴向柱塞泵缝隙高度可变时阀门板上油膜的压力分布.缝隙中油压变化的确定,通常是应用Pasynkow 润滑理论中的Reynolds方程.使用基于有限单元法的自编程序,数值地求解该方程.为了提高结果的精度,基于解的残差估计,应用了加密的自适应网格.给出了依赖于泵的几何条件和工作参数的计算结果.