ORGANO-SOLUBLE FLUORINATED POLYIMIDES DERIVED FROM α,α-BIS(4-AMINO-3,5-DIMETHYLPHENYL)-4'-FLUOROPHENYL METHANE AND VARIOUS AROMATIC DIANHYDRIDES

Organo-soluble fluorinated polyimides were synthesized by the polycondensation of a new aromatic diamine α,α-bis(4-amino-3,5-dimethylphenyl)-4'-fluorophenyl methane with several aromatic dianhydrides.The one-step polymerizationprocedure was conducted at 180℃ in m-cresol,producing the polyimides with inherent viscosities of 0.68-0.76 dL.g^(-1).Thepolyimides could be soluble not only in polar aprotic solvents,such as N-methyl-2-pyrrolidinone,and N,N-dimethylacetamide,but also in common organic solvents,such as chloroform,cyclopentanone,m-cresol and so on.Thepolyimide films show excellent transparency with the UV-Vis cut-off lengths of 310-360 nm and light transmittances ofhigher than 80% in the visible region.In addition,the polyimides exhibit good thermal stability with an initial decompositiontemperature(T_d)higher than 530℃ and have more than 60% of residual weight retentions at 700℃.

Synthesis and Properties of New Fluorinated Polyimides Derived from an Unsymmetrical and Noncoplanar Diamine

A new unsymmetrical and noncoplanar diamine containing trifluoromethyl and trimethyl groups, 1,4-bis（4- amino-2-trifluoromethylphenoxy）-2,3,5-trimethylbenzene （2）, was synthesized using 2,3,5-trimethylhydroquinone and 2-chloro-5-nitrobenzotrifluoride as starting materials. A series of fluorinated poly（ether imide）s （PEIs） （4a-4d） were prepared from diamine 2 with four aromatic dianhydrides via a one-step high-temperature polycondensation procedure. The obtained PEIs were readily soluble in most organic solvents and could be solution-cast into flexible and strong films. The resulting thin films exhibited light color and good optical transparency with a cutoff wave- length of 356--376 nm. They also displayed good thermal stability with glass transition temperatures （Tg） above 281℃, 10% weight loss temperatures in the range of 482--486 ~C, and the weight residue more than 55% at 800℃ in nitrogen. Moreover, they revealed low dielectric constants （2.77-2.93 at 1 MHz） and low moisture absorp- tions （0.41%-0.57%）.

FLUORINATED PHTHALAZINONE-CONTAINING COPOLYIMIDES FOR PASSIVE OPTICAL WAVEGUIDES

A series of fluorinated copolyimides containing phthalazinone moieties were prepared from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride(6FDA),3,3'4,4'-benzophenone-tetracarboxylic dianhydride(BPDA)and2-(4-aminophenyl)-4-[4-(4-aminophenoxyl)phenyl]-2,3-phthalazin-1-one(DHPZ-2NH_2)for making polymeric opticalwaveguides.The resulting copolymers containing 0-50 mo1% BPDA/DHPZ-2NH_2 show good solubility and are soluble insome organic polar aprotic solvents.The copolyimides also present excellent thermal stability.These polymers possess highglass transition temperature higher than 603 K and high decomposition temperature above 742 K determined by differentialscanning calorimetry and thennogravimetric analysis,respectively,under a nitrogen atmosphere.Their refractive indicescould be controlled by varying the ratio of 6FDA and BPDA in the copolymer from 0.5 to 1.0,and the in-plane refractiveindices(n_(TE))range from 1.6366 to 1.6668 and the out-of-plane refractive indices(n_(TM))from 1.6024 to 1.6280 at 632.8 nm.The polymers birefringence(0.0342-0.0388)is almost independent of the 6FDA content of copolymer,which indicated thatthe phthalazinone-containing copolyimides could be suitable to fabricate optical waveguides possessing a low polarizationdependent loss(PDL).

Design of Polarization-independent Wavelength-interleave Coupler in Fluorinated Polyimide Waveguide

Based on the measurement of dispersion characteristic and birefractive index of the fluorinated polyimide film,a statistical optimum design method is proposed and used to realize the design of 32- and 36-wavelengths optical waveguide wavelength-interleave coupler(i,e.,interleaver) with the optimization of polarization fluctuation and wavelength interval of 0.8 nm at 1 550 nm.The largest cross coupling ratios of the two interleavers are respectively less than 1.8% and 3.5%,while the least through coupling ratios are respectively greater than 98.2% and 96.5%.The output differences due to polarization fluctuation are less than ±1.7% and ±3.2%.

New Soluble Polyimides with High Optical Transparency and Light Color Containing Pendant Trifluoromethyl and Methyl Groups

A new aromatic diamine containing trifluoromethyl and methyl groups, namely a,a-bis（4-amino-3-methylphetayl）-4-（trifluoromethyl）phenylmethane （1）, was synthesized from 2-methylaniline and 4-（trifluoromethyl）- benzaldehyde. A series of fluorinated polyimides （PIs） were prepared from the diamine with four commercially available aromatic tetracarboxylic dianhydrides using a one-step high-temperature polycondensation procedure. These obtained PIs showed excellent solubility, with the dissolvability at a concentration of 10 wt% in most solvents, and they could afford flexible and strong films. Thin films of these PIs exhibited high optical transparency and light color, with the cutoff wavelength at 324-357 nm and transmittance higher than 74% at 450 nm. Moreover, these Pls possessed eminent thermal stability and good mechanical properties.

Synthesis and Characterization of Fluorinated Polyimide Derived from 3,3＇-Diisopropyl-4,4＇-diaminodiphenyl- 3＂,4＂-difluorophenylmethane

A novel aromatic diamine monomer, 3,3＇-diisopropyl-4,4＇-diaminodiphenyl-3＂,4＂-difluorophenylmethane （PAFM）, was successfully synthesized by coupling of 2-isopropylaniline and 3,4-difluorobenzaldehyde. The aro- matic diamine was adopted to synthesize a series of fluorinated polyimides by polycondensation with various dian- hydrides： pyromellitic dianhydride （PMDA）, 3,3＇,4,4＇-biphenyltetracarboxylic dianhydride （BPDA）, 4,4＇-oxydiph- thalic anhydride （ODPA） and 3,3＇,4,4＇-benzophenone tetracarboxylic dianhydride （BTDA） via the conventional one-step method. These polyimides presented excellent solubility in common organic solvents, such as N,N-dimeth- ylformamide （DMF）, N,N-dimethyl acetamide （DMAc）, dimethyl sulfoxide （DMSO）, N-methyl-2-pyrrolidone （NMP）, chloroform （CHC13）, tetrahydrofuran （THF） and so on. The glass transition temperatures （Tg） of fluorinated polyimides were in the range of 260--306 ℃ and the temperature at 10% weight loss in the range of 474--502 ℃ Their films showed the cut-off wavelengths of 330--361 nm and higher than 80% transparency in a wavelength range of 385--463 nm. Moreover, polymer films exhibited low dielectric properties in the range of 2.76--2.96 at 1 MHz, as well as prominent mechanical properties with tensile strengths of 66.7--97.4 MPa, a tensile modulus of 1.7--2.1 GPa and elongation at break of 7.2%- 12.9%. The polymer films also showed outstanding hydrophobicity with the contact angle in the range of 91.2°--97.9°.