Search

Summary: Random copolymers of methyl methacrylate (MMA), butyl methacrylate (BMA) and allyl methacrylate (AMA) were prepared via atom transfer radical polymerization (ATRP). AMA is a bifunctional monomer with two double bonds of different reactivity: a highly reactive methacrylate double bond and an allyl ester double bond of lower reactivity. In order to obtain linear polymers with pendant allyl ester groups, the copolymerization conditions have to be optimized with respect to the concentration of AMA, the catalyst system applied – especially the ligand – and the temperature. By means of kinetic studies the reaction parameters for a controlled polymerization were determined. The results obtained show that the higher the temperature and the amount of AMA is the higher is the probability of irregular chain growth and side reactions induced by the pendant allyl ester groups such as hydrogen abstraction from the allyl position or radical addition to the allyl ester double bond. The random copolymers were photochemically crosslinked by using 2,2-dimethoxy-2-phenylacetophenone as photoinitiator. The thermal properties of linear and crosslinked polymers were determined. The glass transition temperatures of both show no significant difference at low AMA content and thus low crosslinking densities. GPC eluograms of MMA/BMA (70:30) copolymers with 5 mol-% AMA at different conversions.

Poly(amide urethane)s were prepared from e-caprolactam, amino alcohols, and diphenyl carbonate or ethylene carbonate in three steps. Polycondensation was performed either with α-hydroxy-ω-O-phenyl urethanes or with α-hydroxy-ω-O-hydroxyethyl urethanes; it was found that the reactivity at 90 °C of the first is much higher than that of the latter. For nearly equal reactivity, the temperature for the polycondensation of α-hydroxy-ω-O-hydroxyethyl urethanes had to be increased from 90 °C to 150 °C. The microstructure of the resulting poly(amide urethane)s differs by the content of urea groups in the polymer chains, which is 5% for poly(amide urethane)s prepared from α-hydroxy-ω-O-phenyl urethanes and 15% for poly(amide urethane)s prepared from α-hydroxy-ω-O-hydroxyethyl urethanes. As a consequence, the thermal properties of the poly(amide urethane)s differ slightly.

Tetramethylene urea (TeU, 1) is successfully copolymerized with 1,2-propylene carbonate (PC, 2), leading to a polyurethane (M n = 12 200; M w 18 400; M w /M n = 1.50) with T m of 145.7°C and a T g of 53.7°C. Mechanistic studies with a blocked isocyanate model compound revealed that, at no stage of the reaction is the TeU ring opened to form an isocyanate. Hence, a well-underlined mechanims for the copolymerized is proposed. Furthermore, TeU, is successfully copolymerized with mixtures of PC and ethylene carbonate (EC, 3). From NMR spectroscopic data of the polyurethanes obtained, it is concluded that PC is less reactive than EC. However, it is possible to increase the PC content in poly(TeU-EC-stat-TeU-PC) by increasing the PC/EC ratio in the feed. 13 C NMR spectroscopy reveals that a random copolymer is obtained. This conclusion is supported by differential scanning calorimetry (DSC) data, which show a continuous decrease in T m with increasing PC content.

Bis(hydroxy)telechic bisphenol A polycarbonate (PC) was prepared via melt polycondensation of bisphenol A (BPA) and diphenyl carbonate (DPC) using lanthanum(m) acetylacetonate as a catalyst for transesterification. Subsequently, the polycarbonate was converted to a bifunctional macroinitiator for atom transfer radical polymerization (ATRP) with the reagent, α-chlorophenylacetyl chloride. The macroinitiator was used for the polymerization of styrene (S) and methyl methacrylate (MMA) to give PS-block-PS and PMMA-block-PC-block-PMMA triblock copolymers. These block copolymers were characterized by NMR and GPC. When styrene and methyl methacrylate were used in large excess, significant shifts toward high molecular weights were observed with quantitative consumption of the macroinitiator. Several ligands were studied in combination with CuCl as the ATRP catalyst. Kinetic studies reveal the controlled nature of the polymerization reaction for all the ligands used.

Poly(esters amide)s from adipic anhydride and α, ω-amino alcohols were obtained by polycondensation of α-carboxyl-ω-hydroxyl amides under mild conditions in solution or by bulk polycondensation at elevated temperatures. For the polycondensation in bulk the influence of catalyst and of temperature on the number-average molecular weight was studied. At a temperature of 170 °C the poly-condensation process is followed by a ring-closing depolymerisation and the formation of cyclic ester amides. Ten- to fourteen-membered cyclic ester amides were obtained and characterized. The ring-opening polymerisation of these cyclic ester amides leads, in a controlled mode, to poly(ester amide)s. The interconversion of poly(ester amide)s and cyclic ester amides by ring-closing depolymerisation and ring-opening polymerisation is possible. The poly(ester amide)s from adipic anhydride and homologous α, ω-amino alcohols H 2 N-(CH 2 ) x -OH (x = 2-6) are semicrystalline materials, their melting points show the odd/even effect observed for [n]-polyamides and [n]-polyurethanes.

The polymerization of 1-hexene with the catalyst systems Cp 2 ZrCl 2 /MAO and Me 2 SiInd 2 ZrCl 2 /MAO is investigated in order to elucidate the nature of the active species in zieconocene/MAO catalyzed polymerizations. Varying monomer concentration and monomer conversion does not result in any unexpected behavior. However, changing catalyst and cocatalyst concentration leads to broadened, or even bimodal, molecular weight distributions under certain reaction conditions. These results may be interpreted in terms of a coexistence of two active species with different rates of propagation and of termination.

In an adiabatic vacuum calorimeter thetemperature dependence of the heat capacity C p 0 of crystalline 2-methyltrimethylene urethane (MTU; systematic name: 5-methylperhydro-1,3-oxazin-2-one) and of amorphous poly(2-methyltrimethylene urethane) 5PMTU; systematic name: poly(5-methyl-2-oxo-1-oxa-3-azahexamethylene)] was studied between 6 and 335 K with an uncertainty of about 0.2%. In a calorimeter with a static bomb and an isothermal shiled the energies of combustion ΔU comb of the monomer and of the polymer were measured. From the experimental data the thermodynamic functions C p 0 (T), H 0 (T)-H 0 (0), S 0 (T), G 0 (T)-H°(0) were calculated in the range of 0 to 340 K, and enthalpies of combustion ΔH 0 comb and thermodynamic parameters of formation ΔH t 0 , ΔS t 0 , ΔG t 0 of the substances studied were estimated at T = 298.15 K and standard pressure. The configurational entropy S 0 conf of the polymer was estimated. The results were used to calculate the thermodynamic characteristics of MTU polymerization in bulk (ΔH 0 pol , ΔS 0 pol , ΔG 0 pol ) with ring-opening and formation of linear PMTU in the range of 0 to 340 K.

Aliphatic [n]-polyurethanes were obtained by catalytic polycondensation of suitable α-hydroxy-ω-O-phenyl urethanes (III). 1H and 13C NMR analyses of the resulting [n]-polyurethanes (3 a–g) show a uniform microstructure consisting of urethane groups only, and with carbonate and urea groups being absent. The [n]-polyurethanes with linear alkylidene moieties (3 a–e) are highly crystalline materials, their melting points show the same odd-even effect as was observed for [n]-polyamides. The [n]-polyurethanes with branched alkylidene groups (3 f, g) show lower crystallinity (3 g) or are amorphous (3 f) materials. Upon heating, the [3]- and all the [4]-polyurethanes (3 a and 3 b, f, g) result in the corresponding cyclic urethanes by ring-closing depolymerization.

In an adiabatic vacuum calorimeter, the temperature dependence of the heat capacity C O p of dimethylene urethane (DMU) and poly(dimethylene urethane) (PDMU) was studied between 6 and 335 K with an uncertainty of about 0.2%. In a calorimeter with a static bomb and an isothermal shield, the energies of ΔU comb of the monomer and of the polymer were measured. From the experimental data, the thermodynamic functions C o p (T), H 0 (T) - H 0 (0), S 0 (T), G 0 (T) - H 0 (0) were calculated in the range from to 335 K, and enthalpies of combustion ΔH 0 comb and thermochemical parameters of formation ΔH 0 f , ΔS 0 f , ΔG 0 f of the substances studied were estimated at T = 298.15 K and standard pressure. The results were used to calculate the thermodynamic characteristics of the ring-opening polymerization of DMU in bulk (ΔH 0 pol , ΔS o pol , ΔG 0 pol ) with formation of linear poly(dimethylene urethane) in the range from 0 to 330 K. In addition, the ceiling temperature T 0 ceil was determined.

The atom transfer radical polymerization (ATRP) of styrene and methyl methacrylate with α,α-dichlorotoluence (DCT) as initiator results in the respective chlorotelechelic polymers. From a kinetic point of view, however, the polymerization of styrene and methyl methacrylate show a different behavior: for the polymerization of styrene DCT is a bifunctional, for the polymerization of methyl methacrylate it is a monofunctional initiator.

ABA type block copolymers with poly[3(S)-isobutylmorpholine-2,5-dione] (PIBMD, A) and poly(ethylene oxide) (M n = 6000, PEO, B) blocks, PIBMD-b-PEO-b-PIBMD, were synthesized via ring-opening polymerization of 3(S)-isobutylmorpholine-2,5-dione in the presence of hydroxytelechelic poly(ethylene oxide) with stannous octoate as a catalyst. M n of the resulting copolymers increases with increasing 3(S)-isobutylmorpholine-2,5-dione content in the feed at constant mole ratio of monomer (M) to catalyst (C) (M/C = 125). No racemization of the leucine residue takes place during both homopolymerization of IBMD and polymerization of IBMD in the presence of PEO and Sn(Oct) 2 . The melting temperature of the PIBMD segments in the block copolymers depends on the length of the PIBMD blocks. The melting temperature of the PEO blocks is lower than that of the homopolymer, and the crystallinity of the PEO block decreases with increasing length of the PIBMD blocks. The PIBMD block crystallizes first upon cooling from the melt. This leads to only imperfect crystallization or no crystallization of the PEO blocks.

The polymerization of N-(hydroxypivaloyl)-e-aminocaproic acid lactone [c(HPv-eAC), 1] a) in bulk at 170°C was found to result in a high molecular weight fraction with M n 20000 (GPC in DMAC, calibration with polystyrene) and an oligomeric fraction depending on the initiator employed. Separation of the polymeric fraction is unsuccessful by using fractional precipitation, however, by means of dialysis a polymeric fraction with a polydispersity index Q < 1.5 was isolated. NMR spectroscopic analysis of the polymer reveals a strictly alternating microstructure with hydroxypivaloyl and e-aminocaproyl repeating units. Regardless of the initiator used no endgroups were detected in both the polymeric and the oligomeric fraction. Even more, GPC analysis of the well resolved oligomeric series reveals the same elution volumes for a given oligomer, regardless of the initiator used. These results led us to conclude that poly(hydroxypivalate-alt-aminocaproate) has cyclic constitution. The glass transition temperature of the semicrystalline polymer is T g = 6,6°C, the melting point T m = 66,6°C. A kinetic study of the polymerization reveals that the monomer conversion does not follow a pseudo first order rate law even at very low conversions. A mechanism for the initiation and the polymerization is discussed.

In an adiabatic vacuum calorimeter the temperature dependence of the heat capacity C 0 p of tetramethylene urethane (TMU) (2-oxo-hexahydro-1,3-oxazepine) and poly(tetramethylene urethane) (PTMU) was studied between 4.3 and 300 K with an uncertainty of about 0.2%. In a calorimeter with a static bomb and an isothermal shield the energies of combustion ΔU comb of the monomer and the polymer were measured. From the experimental data the thermodynamic functions C 0 p , H 0 (T)-H 0 (0), S 0 (T), G 0 (T)-H 0 (0) were calculated in the range of 0 to 300 K, and enthalpies of combustion ΔH 0 comb and thermochemical parameters of formation ΔH 0 f , ΔS 0 f , ΔG 0 f of TMU and PTMU were estimated at T= 298.15 K and standard pressure. The results obtained were used to calculate the thermodynamic characteristics of TMU polymerization in bulk (ΔH 0 pol , ΔS 0 pol , ΔG 0 pol with opening of the seven-membered ring and formation of the linear polymer PTMU, in the range of 0 to 300 K. It was found that the values of the standard Gibbs function of the process (ΔG 0 pol = (-41)-(-42) kJ.mol -1 ) are always negative and do not substantially depend upon temperature in the whole temperature interval studied. This implies that the equilibrium TMU ⇄ PTMU is far on the side of the polymer. The upper (ceiling) limiting temperature of TMU polymerization is T 0 ceil > 1 000 K.

Lipase-catalyzed ring-opening bulk polymerizations of 3(S)-isopropylmorpholine-2,5-dione (IPMD) were investigated. Selected commercial lipases were screened as catalysts for IPMD polymerization at 100°C. Polymerizations catalyzed with lipases PPL, PS, and CR result in IPMD conversions of about 50%, and in molecular weights of the products ranging from 3500 to 17500. Poly(3-isopropylmorpholine-2,5-dione) has a carboxylic acid group at one end and a hydroxyl group at the other end. During the polymerization, racemization of the valine residue takes place. Lipase PPL was selected for further studies. The apparent rate of polymerization increases with PPL concentration and polymerization time. When the PPL concentration is 5 wt.-% and 10 wt.-% with respect to the monomer, a conversion of about 70% is reached after 5 d and 7 d, respectively, while for PPL concentrations of 1 wt.-% and 0.5 wt.-% the conversion is less than 15% even after 11 d. High concentrations of PPL (10 wt.-%) result in high M n values (

Departamento de Ingenieri´a Qui´mica, Universidad Polite´cnica de Catalun˜a,E. T. S. de Ingenieros Industriales, Diagonal 647, 08028 Barcelona, Spain(Received: October 2, 1998; revised: November 26, 1998)SUMMARY: Two heterotelechelic poly(ethylene glycol)s were synthezised by end group modification of a-hydro-x-hydroxy-poly(oxyethylene) (PEG). The first reaction route starts from heterobifunctionala-hydro-x-octadecanoyloxy-poly(oxyethylene) (400) and comprises the synthesis ofa-hydro-x-carboxymethoxy-poly(oxyethylene). The second pathway starts from homotelechelic PEG(400) and leads to a-(2-propenyl)-x-carboxymethylthio-poly(oxyethylene). Purification of the desired products was accomplished by means ofion exchange chromatography on DEAE Sephadex. PEG derivatives were characterized by means of NMR,IR, HPLC and GPC. MALDI-TOF-MS recorded in the reflectron mode served as a fine method that providesinformation on chemical composition as well as molecular weight.

The synthesis of cyclo(amide-ester)s based on α-amino acids and e-aminocaproic acid in combination with β-hydroxy acids was achieved by ring-expansion reactions. Three different approaches were followed: (i) According to Shemyakin, e-caprolactam or diketopiperazines were acylated with differently substituted β-benzyloxyacyl chlorides. Removal of the protecting group by hydrogenolysis over a palladium catalyst results in hydroxyacyl incorporation into the e-caprolactam or the diketopiperazine ring and formation of the eleven-membered cyclo(amide-ester)s 1 a–c or the fourteen-membered cyclo(diamide-diester)s 2 a–c. (ii) Alternatively, the cyclo(amide-ester)s 1 a–c were obtained via intramolecular nucleophilic substitution of the halogen atom in N-(3-halogenoacyl)-e-caprolactam by the oxygen atom of the lactam unit followed by reaction with water. (iii) Finally, results on the intramolecular Michael addition in N-(acryloyl)- and N-(crotonyl)-e-caprolactams are presented. The Michael addition was induced by the nucleophilic addition of the lactam oxygen atom to the CC double bond followed by a sequence of reactions, which leads to the cyclo(amide-ester)s 1 a, b.

N-(3-Hydroxypropionyl)-e-aminocaproic acid lactone [c(3HP-eAC), 1] was polymerized in dimethylformamide solution with dibutyldimethoxytin as initiator at 100°C. A strictly alternating poly(amide-ester), poly(3-hydroxypropionate-alt-e-aminocaproate), was obtained, a semicrystalline polymer with a melting point of 145.9°C. The polymerization was found to proceed via a tin alcoholate active species as was deduced from 'H NMR endgroup analysis of the polymer quenched with water. In addition, the active chain ends were quenched with diphenyl chlorophosphate and analyzed by means of 31 P NMR spectroscopy; a diphenylalkyl phosphate was identified, proving the alcoholate active site. The polymerization follows a pseudo-first order rate law only at low conversions. However, a linear dependence of the number-average molecular weight on conversion was found, proving that transfer reactions play a minor part throughout the polymerization process. A mechanism for the initiation and propagation is proposed.

A blend of polycaprolactone (PCL) and poly(2,2-dimethyltrimethylene carbonate) (PDTC) containing catalytic amounts of dibutyltin dimethoxide was prepared from solution. The blend was then subjected to melt-mixing at 200°C and samples were taken after different times. According to thermal analysis data, with the increase of reaction time a gradual loss of the crystallizability of the blend components is observed, and after 70 min at 200°C the system becomes completely amorphous. 13 C NMR data suggest that the loss of crystallizability of the blend is accompanied by an abrupt decrease in PCL and PDTC sequence lengths reaching after 70 min at 200°C an average length of about two repeating units each. These effects are explained by transesterification reactions between the lactone and carbonate units.

A process for preparing optically active 2,5-morpholinediones 1 is described starting from optically active α-amino acids and optically active α-hydroxy esters. The process involves three steps: In the first step the sodium salt of an α-amino acid is condensed with an α-hydroxy ester to yield an optically active N-(α-hydroxy acyl)-α-amino acid 4. In the second step the hydroxy acid obtained is subjected to esterification with ethanol. In the third step the N-(α-hydroxy acyl)-α-amino acid ethyl ester 5 is subjected to cyclization with an acidic catalyst. For some examples the cyclization was also performed directly from the hydroxy acid 4. Morpholinediones 1 are useful as precursors for the preparation of poly(depsipeptides) 2 and copolymers containing depsipeptide repeating units.

Polymerization of (3S,6S)-3-isopropyl-6-methyl-2,5-morpholinedione (1) with tin octoate (Sn(oct) 2 ) and tin acetylacetonate (Sn(acac) 2 ) results in an alternating polymer with lactic acid and valine repeating units, poly[(S)Lac-alt-(S)Val] (2). From time dependent analysis of the monomer conversion and the number average molecular weight of the polymer it is concluded that Sn(oct) 2 acts as a catalyst and Sn(acac) 2 as an initiator. From 'H NMR spectroscopic analysis of the polymer 2 it is concluded that the lactate moiety suffers from racemization during polymerization, while the valine moiety does not. The number ratio of not racemized repeating units (S,S) and racemized repeating units (R,S) in the polymer was calculated to be 11.5 for the polymer prepared with Sn(oct) 2 as a catalyst and 18.9 for the polymer prepared with Sn(acac) 2 as an initiator.

The ring-opening polymerization of 2,2-dimethyltrimethylene urethane (DTU, 1) is a thermodynamically disfavoured process. According to calorimetric measurements by Lebedev et al., the Gibbs energy of polymerization in bulk varies between 29 kJ. mol -1 and 23 kJ. mol -1 . Poly(DTU) (2) was synthesized by polycondensation of an activated dimeric hydroxyurethane (DDPP, 3) in an end group selective reaction. The selectivity of the polycondensation is influenced by temperature and the catalyst chosen, and best results were obtained at 120°C employing Bu2Sn(OOC-(CH 2 ) 10 -CH 3 ) 2 as a catalyst, which favours end group reaction rather than intramolecular transurethanization. Poly(DTU) (2) was degraded at 120°C in a closed system to yield a mixture containing 94 wt.-% of DTU and 6 wt.-% of oligomers. The depolymerization proceeds via formation of cyclic oligomers as intermediates.

Cyclic diurethanes of AA/BB type 3a-d were prepared starting from the diamines 1,2-diaminoethane (1a), 1,3-diaminopropane (1b), l,3-diamino-2,2-dimethylpropane (1c), 1,4-diaminobutane (1d) and 2,2-dimethyltrimethylene bis(chloroformate) (2) under high dilution conditions. The NMR spectroscopic characterization of the cyclic diurethanes reveals a highly rigid conformation of the diurethane cycles. Upon interfacial polycondensation the starting materials result in polyurethanes 4a-d. Gel-permeation chromatography (GPC) reveals the multimodal distribution of the polymers: beside high molecular weight material low molecular weight cyclic oligomers are observed in appreciable amount. Ring-opening polymerization of the diurethanes 3a-c results in cyclic ureas 6a-c and 2,2-dimethyltrimethylene carbonate (DTC), respectively, oligomers formed from DTC. Ring-opening polymerization of the cyclic diurethane 3d in the melt or in solution with various nucleophilic initiators results in polyurethane 4d. NMR spectroscopic analysis of polyurethane 4d reveals that beside urethane groups carbonate and urea groups are present, their concentration being dependent on the initiator used and the polymerization conditions applied. The polyurethane 4d obtained by ring-opening polymerization does not contain cyclic oligomers.

The polymerization of 2-acetoxymethyl-2-alkyltrimethylene carbonates (alkyl = methyl : AMTC, alkyl = ethyl : AETC) and of 2-methoxycarbonyl-2-methyltrimethylene carbonate (MMTC) in toluene with see-butyllithium as initiator results in the respective polymer with yields between 78% and 88%. The analysis of the polymer microstructure by means of NMR spectroscopy reveals linear chains without branching due to an attack of the active chain end at the ester moiety of the repeating units. Poly(MMTC) and poly(-AETC) afford crystalline materials upon precipitation from solution while poly- (AMTC) is amorphous ; after quenching from the melt all materials are amorphous. Copolymerization of AMTC, AETC and MMTC with 2,2-dimethyltrimethylene carbonate (DTC) results in random copolymers. The kinetics of the polymerization of AETC and MMTC revealed that the ester side chain enhances the rate of propagation compared to the polymerization of DTC. The apparent rate constants of propagation in toluene with lithium alcoholate as active sites at 23°C were determined to be k app DTC = 4. 10 -3 s -1 , k app AETC = 4,28. 10 -2 s -1 , and k app MMTC = 2,57. 10 -2 s -1 . Studies of ring-chain equilibria in solution of tetrahydrofuran revealed that on the basis of the theory of Jacobson-Stockmayer the characteristic ratios of the polymers are C∞ PDTC = 7,1, C∞ PMMTC = 8,6, C∞ PAETC = 9,9, and C∞ PAMTC = 13,4.

Bis(hexamethylene carbonate) (HC) and bis(2,2,3,3,4,4,5,5-octafluorohexamethylene carbonate) (FHC) were synthesized starting from the corresponding diols and diphenyl carbonate in a two-step reaction : (i) first polycondensation occurs, (ii) then ring-closing depolymerization leads to HC and FHC, respectively. The polymerization of HC is performed with sec-butyllithium in toluene solution, and the corresponding polymer is obtained in high yield. Polymerization of FHC is perfomed either in tetrahydrofuran solution with dibutylmagnesium as initiator or in the melt with dibutyltin dimethoxide as initiator. Poly(HC) is a semicrystalline polymer with a melting point of 54.0°C and a glass transition temperature of -51.3°C. Poly(FHC) was obtained either as a semicrystalline material with a melting point of 40.8°C or an amorphous material with a glass transition temperature of -39.8°C. Copolymers of HC and FHC with a diad ratio of 19 : 60 : 21 were obtained by melt polymerization with dibutyltin dimethoxide as initiator. The ring-chain equilibrium established during polymerization was studied for HC in toluene solution and for FHC in the melt. The concentration of the cyclic oligomers at equilibrium was determined, and for poly(HC) the characteristic ratio was calculated to be 10.0 ± 1.0.

Poly(L-lactide)-block-poly(L-amino acids) block copolymers were prepared via polymerization of α-amino acid N-carboxyanhydrides with amino-terminated poly(L-lactide)s as macroinitiators. Two types of macroinitiators were used, one with an aminopropoxy head group (number-average molecular weight M n = 22000) and the other one with a phenylalanine end group (M n = 18000). The first macroinitiator was obtained by polymerization of (L,L)-lactide with an initiator prepared in situ from diethylzinc Et 2 Zn and N-tert-butoxycarbonyl-1-amino-3-propanol, followed by deprotection of the amino group. The second macroinitiator was obtained by endcapping of poly(L-lactide) with N-tert-butoxycarbonylphenylalanine and deprotection of the amino group. 1 H- and 13 C NMR spectroscopies confirm the block structure of the copolymers obtained. In differential scanning calorimetry curves only one melting transition characteristic of the poly(L-lactide) block is observed, on further heating decomposition occurs. By thermogravimetry two steps of decomposition are observed, the first one being assigned to the decomposition of the poly(L-lactide) block, and the second one to that of the poly(amino acid) block, by comparison with the thermal behaviour of the corresponding homopolymers.

2-Cyano-2-methyltrimethylene carbonate (CMTC, 2) was synthesized starting from 2-methylacrolein (6), propionaldehyde (8) or 2-hydroxymethyl-2-methyl-1,3-propanediol (9). A key position in this synthesis is held by 2,2-bis(hydroxymethyl)propionitrile (3), which in a first step, is reacted - in conjunction with 2,2-dimethyl-1,3-propanediol (20) - with diphenyl carbonate (17) to result in a statistical copolycarbonate. Ring-closing depolymerization of this polymer, with a catalyst based on tin, yields in a second step the title monomer, CMTC (2), along with 2,2-dimethyltrimethylene carbonate (DTC, 1a). Separation of the two monomers can be achieved by selective solubilization of the latter in toluene. Polymerization of CMTC is performed preferentially by using weak nucleophiles as initiators, such as Et 2 AlOEt, Al(O-secBu) 3 or MgBu 2 , since strong nucleophiles such as BuLi or ZnEt 2 tend to give side reactions with the cyano group. Copolymerization of CMTC with DTC results in statistical copolymers. With Et 2 AlOEt as initiator copolymers with Bernoulli statistics are obtained, with a ratio of diads DTC/DTC : (DTC/CMTC + CMTC/DTC) : CMTC/CMTC equal to 1 :2 :1 for equimolar feed composition. With MgBu 2 as initiator and the same feed composition, a copolymer with the diad ratio 1 :5 :1 is obtained. Poly(CMTC) is a crystalline polymer with a melting point of 132.9 °C and a glass transition temperature of 68.8 °C.

Ring-closing depolymerization of poly(e-caprolactone) in toluene solution with catalytic amounts of Bu 2 Sn(OMe) 2 results in a mixture of cyclic oligomers, the equilibrium concentration of which corresponds to the concentration predicted according to the Jacobson-Stockmayer theory. e-Caprolactone, however, is absent from this reaction mixture. When poly(e-caprolactone) is depolymerized in the melt at 260 o C in the presence of a catalyst, beside e-caprolactone its cyclic dimer and trimer are distilled off. The composition is dependent on the catalyst used, e. g., Bu 2 Sn(OMe) 2 produces 95,4 wt.-% of e-caprolactone and 3,7 wt.-% of its dimer while with Ti(OiPr) 4 (iPr: isopropyl) 51,4 wt.-% e-caprolactone and 49,6 wt.-% of its dimer are obtained. Block copolymers containing poly(e-caprolactone) result in a similar product distribution, however, the second block may influence the rate of decomposition. The activation energy of the catalysed (0,5 mol-% Bu 2 Sn(OMe) 2 ) and uncatalysed ring-closing depolymerization were determined to be 63 kJ/mol and 87 kJ/mol, respectively

Two new homologous series of semiflexible main-chain polyesters on the basis of 4-hydroxy-and 4-carboxycinnamic acid in conjugation with 2-tert-butylhydroquinone and alkylene spacers with 3 to 8 methylene groups were prepared by low-temperature solution condensation. The thermotropic properties were investigated by means of differential scanning calorimetry, polarising microscopy and X-ray diffraction analysis. The differences in enantiotropic behaviour and thermal stability of the mesophases influenced by the two different linkage groups between alkylene spacer and rigid moiety are discussed in comparison to related systems known from the literature.

The polymerization of 2,2-dimethyltrimethylene carbonate (DTC, 1) with tri-sec-butoxyaluminium (Al(O-sec-Bu)3) proceeds with suppression of macrocyclics formation. The propagation of the polymerization proceeds pseudoanionically via insertion. Within the scope of a kinetic treatment, the time-conversion relationship was determined for the polymerization of DTC with Al(O-sec-Bu)3 as initiator and toluene as solvent. For a polymerization temperature between 15°C and 74°C, the apparent rate constant was found to be between 0,1 and 1,0 L · mol−1 · s−1. Using the Arrhenius plot the experimental temperature coefficient (20,6 kJ · mol−1) as well as the frequency factor of the polymerization (1,3 · 103 L · mol−1 · s−1) were determined. Investigation of the dependence of the rate of polymerization on the initiator concentration revealed a degree of aggregation of 2 for the active species.

Thermoplastic elastomers with ABA-block structure, A representing the hard segment and B the soft segment, were prepared by ring-opening polymerization from 2,2-dimethyltrimethylene carbonate (DTC, 1) and e-caprolactone (ECL, 2) as monomers. Typical anionic initiators, viz. the dilithium salt of hydroxytelechelic poly(ethylene oxide) 200 (4) and of polytetrahydrofuran 1000 (5) and as an insertion initiator the bis(diethylaluminium) salt of triethylene glycol were used. The soft block is formed by a sequence of random (or tapered) structure comprising equimolar amounts of the two monomers and obtained by simultaneous polymerization of DTC and ECL. The hard blocks consist of highly crystalline poly(2,2-dimethyltrimethylene carbonate) sequences. The thermal properties of the polymers depend on the sequence length, the content of heterodiads in the soft block and the thermal history of the samples. Copolymer films with short end blocks and high content of heterodiads show rubber-elastic properties at normal conditions.

This paper describes the synthesis of polymers having spiro orthoester side groups, starting from lactones with methacrylate side groups. The spiro orthoester polymers are synthesized by a reaction with an oxirane. The hydroxy-functional lactones 3-hydroxy-4,4-dimethyl-2-oxotetrahydrofuran (1) and 5-hydroxymethyl-2-oxotetrahydrofuran (13) were esterificated with methacryloyl chloride. The esterification of 5-oxotetrahydrofuran-2-carboxylic acid (6) and 2,2-dimethyl-5-oxotetrahydrofuran-3-carboxylic acid (11) with 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate yielded the functionalized precursors for the synthesis of polymeric spiro orthoesters. These monomers were polymerized and copolymerized with methyl methacrylate and characterized. Furtheron, the obtained polymers with lactone groups were converted to the corresponding spiro orthoesters using 2,3-epoxypropyl phenyl ether in the presence of boron trifluoride.

For some cyclic aliphatic urethanes (dimethylene urethane, trimethylene urethane, 2-methyltrimethylene urethane, 2,2-dimethyltrimethylene urethane, tetramethylene urethane) and the corresponding linear polyurethanes (poly(dimethylene urethane), poly(trimethylene urethane), poly(2-methyltrimethylene urethane), poly(2,2-dimethyltrimethylene urethane), poly(tetramethylene urethane)) the temperatur dependence of the heat capacity, C p 0 , were investigated in the range of 5-10 K to 300-450 K, and temperatures and enthalpies of physical transitions were determined at standard pressure. From the experimental data the standard thermodynamic functions, i.e. enthalpies H 0 (T)-H 0 (0), enropies S 0 (T), and Gibbs functions G 0 (T)-H 0 (0) were calculated in the range of 0 to 300-450 K for all compounds studied. The configuational entropies, S 0 conf , of the polymers in the glassy and partly crystalline state were estimated. The energies of combustion of the substances were determined experimentally and the standard enthalpies of combustion Δ comb H 0 and thermodynamic parameters of formation Δ f H 0 , Δ f S 0 , Δ f G 0 , were calculated at T = 298.15 K. The results obtained were used to calculate the standard thermodynamic parameters of ring-opening polymerization of cyclourethanes in bulk wtih in the range of 0 to 300-450 K. From the thermodynamic functions, the energies of combustion and the thermodynamic parameters of formation of cyclic monomers and polymers, and the dependence of the above properties on the chemical structure of the compounds were obtained. Estimations of the corresponding properties were made for the monomers and polymers not yet studied experimentally.